简单问题,请指点

Public Function IsFileExist(fstrFileName As String) As Boolean
Dim hFile As Integer
If(fstrFileName = "") Then
IsFileName = False
Exit Funtion
Else
hFile = FreeFile()
Open fstrFileName For Input Access Read As #hFile
Close #hFile
End If
End Funtion
这个函数是用来判断文件是否存在的.
可是这几句我不明白,谁能给解释一下,谢了,
hFile = FreeFile()
Open fstrFileName For Input Access Read As #hFile
Close #hFile