Just for future reference:
Transom: a bar of wood or stone across the top of a door or window, also a fixed window over a door or another window.
Threshold: 1. A piece of wood or stone placed beneath a door; a doorsill. 2. An entrance or a doorway.
Transition: To change from one thing to another (one kind of flooring, or level of flooring)
Look at: http://www.woodfloorsonline.com/prod..._hardwood.html
Very good explanations of different situations with new floors, moldings, and transitions.