What is "InvokeRequired " about, and what does "BeginInvok e" do?

[Curious]

I have the following code:

if (this.InvokeReq uired)
{
IAsyncResult result = this.BeginInvok e(new
EventHandler(th is.UpdateButton s),
new object[] { this, EventArgs.Empty });

while ((!result.IsCom pleted) &&
(result.AsyncWa itHandle.WaitOn e(100, false)))
{
//Waitting for the asynch call to complete.
}
this.EndInvoke( result);
}
else
{
UpdateButtons(t his, EventArgs.Empty );
}

Could anyone tell me what "InvokeRequired " is about, and what
"BeginInvok e" does?

Thanks!

[Curious]

Thanks for the explanation! It's clear.

The online help is not nearly as clear as yours.