DEFINITION: Different between Delegate.BeginInvoke and Thread.Start()

If I have a method of type

public void myMethod()
{

}

And I create a delegate void NewDelegate(void)

What is the actual difference between the following calls and how they are handled by .NET and the OS

NewDelegate del = NewDelegate(myMethod);
del.BeginInvoke(null, null);

and

Thread t = new Thread(new ThreadStart(myMethod));
t.Start();

I know the delegate will use a thread from the thread pool, but will the thread t as well?  What is the actual effect of one versus the other.