I'm not going to post all the ins and outs here, but basically it is a card-trading game (much like the Pokemon/Yugioh type stuff etc). You have a deck of cards with mechs and special abilities on them.
When you instigate a challenge with an opponent, this sandbox grid is laid out with bases on each end. You use your cards to summon mechs on to the battle grid. (Don't bother trying to figure out how this happens, it just happens.)
Each player takes in turns to move mechs and play cards. You use your units, and any special ability cards, to attack your opponent's mechs and base. The winner gets to take an opponent's card, allowing them to have a better deck of cards and thus be a more challenging opponent.
When you instigate a challenge with an opponent, this sandbox grid is laid out with bases on each end. You use your cards to summon mechs on to the battle grid. (Don't bother trying to figure out how this happens, it just happens.)
Each player takes in turns to move mechs and play cards. You use your units, and any special ability cards, to attack your opponent's mechs and base. The winner gets to take an opponent's card, allowing them to have a better deck of cards and thus be a more challenging opponent.