[mavrick0]

BEC is the short form for battery eliminator circuit. Way back you use to have to run a separate battery pack to supply power to the receiver and servos. Then they came out with BEC's, some built into the receivers, some built into the on/off switch but are now only in the ESC. So if PMD gives you the choice if you want to run power to the receiver from the ESC you get the one with the BEC. If you are running your receiver from a separate supply you'd buy the one without a BEC.
Now as for the full forward and reverse. Some ESC's will only give you 50% reverse and that's all but with PMD's they give you 100%. That's all that means but it will still be graduated.