When you give someone a flower or a friendship bracelet or something symbolic of the way you feel about them, you're giving them a token of your affection.
A token is not only something sentimental (like a keepsake) or symbolic (like your friendship bracelet). You, yourself, can also be a token: If you're the only female in your office, for instance, and you were hired just so there'd be at least one woman, then you're the "token female." Tokens can also be a kind of special currency, like the coins you use in slot machines. Before the Metro Card, New York City subway riders paid their fares with tokens.