what is this profile when using MAPI

hi people, in my VB application, i use MAPI to try to send emails .below are the coding i used:

Private Sub cmdSend_Click()
With MAPIMessages1
.MsgIndex = -1
.RecipDisplayName = txtSendTo.Text
.MsgSubject = txtSubject.Text
.MsgNoteText = txtMessage.Text
.SessionID = MAPISession1.SessionID
.Send
End With
MsgBox "Message sent!", , "Send Message"

End Sub

Private Sub Form_Load()
MAPISession1.SignOn

End Sub
Private Sub Form_Unload(Cancel As Integer)
MAPISession1.SignOff
End Sub

when i run the program, it ask me to choose profile. can anyone tell me what is this all about...thanks

catgirl