What's the difference?

What's the difference between:

* ^from:.*daemon

and:

* ^from_daemon

Also between:

* ^tojack

and:

* ^to:.*jack

Also, if I wanted to catch:

Bill Jackson <jack(_at_)nowhere(_dot_)edu>

Would any of the following *not* work?:

^fromjack
^from:.*jack
^from_bill
^from: bill jackson

Note: on the last, would rephrasing it to:

^from: Bill Jackson*

Make any difference?

Thanks for any help!

Luke