This is my first ever CCG/LCG and I am not familiar with the terms Rotation and Draft(or Draft Cube). Can anyone give a brief deffinition?

"Rotation" refers to the card set that is currently legal to use in organized tournaments. Its a way of phasing out older cards, every three years or so, so that new players don't have to buy old cards for ridiculous prices, and to maintain balance.

"Draft" is a way of running a tournament, where players open booster packs, and choose what cards they want to make their decks out of, emphasizing lesser used cards over powerful rares.

A "Draft Cube" is a way of trying to artificially create a "draft" with a fixed card pool. Since AGoT no longer has booster packs, a "draft cube" would be used to pretend that you can still "draft."