Your base sits on one side, the enemy's on the other, and the battle is decided by which one gets destroyed. Clash of Tanks is a real-time strategy game, so there are no turns: you deploy tanks and the fight keeps moving.
The decision that matters most is the pick. Every tank has its own strength and its own weakness, so no single unit wins on its own. Choosing the right type at the right moment is, according to the publisher, the best way to win the battle. If you like this kind of tank fight, Stick Tank Wars is another tank game in the action section.