Okay, I'll give you a description of them.
Mage nuker[
A mage who uses all their abilities at once, oftenly all their abilities are offensive. They use them to immediatly stun, deal damage, and deal even more damage during a very short time period.
Mage supporter
A mage with supportive abilities oftenly accompanied with one or two offensive. Supportive such as slowing the opponents down, stun them, haste on your teammates, defense, etc.
Tank
Already explained.
Melee DPS
They are so/so fragile and deal a hefty sum of damage. Quickly slaying the reckless.
Ranged DPS
Oftenly alot weaker but other than the range and the included weakness not much different from a melee DPS.
Ganker
Low health, extremely high damage, is what a ganker is. Easy to target but they usually have a way or two to escape.
Tank supporter
A tank with more buffing ways. Like a mage supporter.
Tank DPS
Half tank half DPS.