Don't be put off by the acronyms and travel-speak. The most important distinction is between miles that get you closer to some kind of elite status on a frequent flier program and those that can be redeemed for various goodies (such as free trips and upgrades). On this board the first are referred to as Elite Qualifying Miles (EQM's) and the second are Reedemable Miles (RDM's). For your purposes they're the same thing -- if you fly US Airways and your United Mileage Plus number is entered on the reservation (check your boarding pass), you will get miles that count toward status on United and can be banked and redeemed later for trips on United.

By the way, if you think you have already entered your United number but it's not showing on your US Airways boarding pass, go to a customer service agent, at checkin or at the gate, ask that person to enter it, and reprint the boarding pass. I've had trouble with the US Airways system ever since the merger with American West.