Token
Tokens are markers on cards that serves as a counter. Some cards might start with a specific number of tokens or might start with zero. Actions by the card or against the card may add or remove tokens as they occur.
When the card hits a specific number of tokens, it's possible that a final action (like sending the card to timeout) occur. In other cases, tokens might be used to keep track of a number that is used in conjunction with another card's action.
Tokens of different names do not mix, and it's possible that a card might have multiple types of tokens on them at the same time. Keeping track of which token is which and what count they are at might be important.
Although tokens might be given names based on the card, (for example "Book Tokens" on The Library), the tokens themselves can be physically anything.