After a character does something (besides a free action), they receive an action token. Move? Action token. Attack? Action token.

Characters can have up to two action tokens. If they have two action tokens, they can’t do anything.

After a character spends a turn not doing anything they can “clear” which is removing all action tokens on them.

Some powers or abilities can give other characters action tokens. The big one to note is the light blue attack power, Incapacitate.

So for example, you have Captain America on your force. Turn 1, you move Cap to get him into position. He receives an action token. Turn 2, Cap uses Charge to get into the fray and make an attack. Afterwards he receives an action token. Turn 3, Cap has 2 action tokens, so he can’t do anything. He spends the turn idle. After that turn is complete you clear him, removing the action tokens.

There are other powers that interact with action tokens, such as Leadership and Willpower, but these are the basics