What does it mean by " <STAThread()> _"

[bnathvbdotnet]

<STAThread()> _
Shared Sub Main()
Application.Run(New Customers)
End Sub 'Main

Customer is the name of the windows form

I read some thing in help in regards to COM Interop..but in easy words what does STAThread mean?

Any explanation is very helpful.

thanks
nath