关于class(TComponent),求教各位大哥！

[bmbmbm123delphi]

今天老师考给我一个程序，里面有些类在定义的时候是这种形式：Txxx=class(TComponent),我不知道用这种方法定义的类什么特点，怎么使用。。。附一小段程序：
TCustomMomSendClient = class(TComponent)
private
FRecpThread: TRespThread;
FPeerPort: Integer;
FPeerCode: String;
FPeerIP: String;
FTCPClient: TIDTCpClient;
procedure SeTRespThread(const Value: TRespThread);
procedure SetPeerCode(const Value: String);
procedure SetPeerIP(const Value: String);
procedure SetPeerPort(const Value: Integer);
procedure SetTCPClient(const Value: TIDTCpClient);
function Get_TCPClient: TIDTCpClient;
function Get_RecpThread: TRespThread;
{ Private declarations }
protected
{ Protected declarations }
procedure OnConnected(Sender: TObject);Virtual;
procedure OnDisconnected(Sender: TObject);Virtual;
public
{ Public declarations }
Destructor Destroy;Override;
Function DoSend(AMsgStr :String) :Integer;
Property TCPClient :TIDTCpClient read Get_TCPClient write SetTCPClient;
Property RecpThread :TRespThread read Get_RecpThread write SeTRespThread;
published
{ Published declarations }
Property PeerCode :String read FPeerCode write SetPeerCode;
Property PeerIP :String read FPeerIP write SetPeerIP;
Property PeerPort :Integer read FPeerPort write SetPeerPort;
end;