EQM = Elite Qualifying Miles (Medallion QM on DL) that show how many miles you've flown on a carrier since Jan 1 of each year. They reset next Jan 1 and are used to determine your elite status for the next 12 months. Almost every US carrier has something like this:
<25k=General Member
25-49999=Silver
50-74999=Gold
>75k=Platinum
with the exception of UA, where the "Platinum" is at 100K (hence the term 1K)

RDM are redeemable miles that you can spend on upgrades, award tickets, etc. These don't reset at the end of the year, but they might expire after a certain time. Most airlines give you an RDM bonus ion flights f you are elite. You can also earn RDM with credit cards, hotel stays, car rentals, blah blah blah, depending on the program. The FT forums for each program will give you more details.

So, you can see why it's a good idea to stick with one airline whenever possible - you earn more EQM toward your elite status, and get the RDM bonus as well. Having about 10k EQM on 3 different carriers is not really a good thing, but having 30+k EQM on one carrier is better.

trekwars: it might also help you to look in the FAQ section of one of the airline forums for answers to a lot of these "beginner" questions. ^