求解释--vnd.android.cursor.dir与vnd.android.cursor.item究竟该怎么区分？？

最近在看NotePad案例但是不理解vnd.android.cursor.dir与vnd.android.cursor.item的使用场合有什么不同？求解释。。。
以下是官方的案例解释：
Note Pad Example
The Note Pad sample application enables users to browse through a list of notes, view details about individual items in the list, edit the items, and add a new item to the list. This section looks at the intent filters declared in its manifest file. (If you're working offline in the SDK, you can find all the source files for this sample application, including its manifest file, at <sdk>/samples/NotePad/index.html. If you're viewing the documentation online, the source files are in the Tutorials and Sample Code section here.)

In its manifest file, the Note Pad application declares three activities, each with at least one intent filter. It also declares a content provider that manages the note data. Here is the manifest file in its entirety:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.notepad">
<application android:icon="@drawable/app_notes"
android:label="@string/app_name" >

<provider android:name="NotePadProvider"
android:authorities="com.google.provider.NotePad" />

<activity android:name="NotesList" android:label="@string/title_notes_list">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.EDIT" />
<action android:name="android.intent.action.PICK" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.GET_CONTENT" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
</activity>

<activity android:name="NoteEditor"
android:theme="@android:style/Theme.Light"
android:label="@string/title_note" >
<intent-filter android:label="@string/resolve_edit">
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.EDIT" />
<action android:name="com.android.notepad.action.EDIT_NOTE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.INSERT" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />
</intent-filter>
</activity>

<activity android:name="TitleEditor"
android:label="@string/title_edit_title"
android:theme="@android:style/Theme.Dialog">
<intent-filter android:label="@string/resolve_title">
<action android:name="com.android.notepad.action.EDIT_TITLE" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.ALTERNATIVE" />
<category android:name="android.intent.category.SELECTED_ALTERNATIVE" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
</activity>

</application>
</manifest>

The first activity, NotesList, is distinguished from the other activities by the fact that it operates on a directory of notes (the note list) rather than on a single note. It would generally serve as the initial user interface into the application. It can do three things as described by its three intent filters:

<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>

This filter declares the main entry point into the Note Pad application. The standard MAIN action is an entry point that does not require any other information in the Intent (no data specification, for example), and the LAUNCHER category says that this entry point should be listed in the application launcher.

<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.EDIT" />
<action android:name="android.intent.action.PICK" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />
</intent-filter>

This filter declares the things that the activity can do on a directory of notes. It can allow the user to view or edit the directory (via the VIEW and EDIT actions), or to pick a particular note from the directory (via the PICK action).

The mimeType attribute of the <data> element specifies the kind of data that these actions operate on. It indicates that the activity can get a Cursor over zero or more items (vnd.android.cursor.dir) from a content provider that holds Note Pad data (vnd.google.note). The Intent object that launches the activity would include a content: URI specifying the exact data of this type that the activity should open.

Note also the DEFAULT category supplied in this filter. It's there because the Context.startActivity() and Activity.startActivityForResult() methods treat all intents as if they contained the DEFAULT category — with just two exceptions:
Intents that explicitly name the target activity
Intents consisting of the MAIN action and LAUNCHER category

Therefore, the DEFAULT category is required for all filters — except for those with the MAIN action and LAUNCHER category. (Intent filters are not consulted for explicit intents.)

<intent-filter>
<action android:name="android.intent.action.GET_CONTENT" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>

This filter describes the activity's ability to return a note selected by the user without requiring any specification of the directory the user should choose from. The GET_CONTENT action is similar to the PICK action. In both cases, the activity returns the URI for a note selected by the user. (In each case, it's returned to the activity that called startActivityForResult() to start the NoteList activity.) Here, however, the caller specifies the type of data desired instead of the directory of data the user will be picking from.

The data type, vnd.android.cursor.item/vnd.google.note, indicates the type of data the activity can return — a URI for a single note. From the returned URI, the caller can get a Cursor for exactly one item (vnd.android.cursor.item) from the content provider that holds Note Pad data (vnd.google.note).

In other words, for the PICK action in the previous filter, the data type indicates the type of data the activity could display to the user. For the GET_CONTENT filter, it indicates the type of data the activity can return to the caller.

Given these capabilities, the following intents will resolve to the NotesList activity:

action: android.intent.action.MAIN
Launches the activity with no data specified.
action: android.intent.action.MAIN
category: android.intent.category.LAUNCHER
Launches the activity with no data selected specified. This is the actual intent used by the Launcher to populate its top-level list. All activities with filters that match this action and category are added to the list.
action: android.intent.action.VIEW
data: content://com.google.provider.NotePad/notes
Asks the activity to display a list of all the notes under content://com.google.provider.NotePad/notes. The user can then browse through the list and get information about the items in it.
action: android.intent.action.PICK
data: content://com.google.provider.NotePad/notes
Asks the activity to display a list of the notes under content://com.google.provider.NotePad/notes. The user can then pick a note from the list, and the activity will return the URI for that item back to the activity that started the NoteList activity.
action: android.intent.action.GET_CONTENT
data type: vnd.android.cursor.item/vnd.google.note
Asks the activity to supply a single item of Note Pad data.
让人想不明白的是：
1、为什么<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.EDIT" />
<action android:name="android.intent.action.PICK" />
对应的是
<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />
而 <action android:name="android.intent.action.GET_CONTENT" />
却对应
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
按理说编辑的、查看的、以及获取的数据都应该是一条数据，而不是采用vnd.android.cursor.dir，想了很久想不明白，故求救于个位道友