If a Hunter is bitten by Dracula or a vampire, the player is given a Bite token. While under the effects of a bite, certain event cards (marked "Bitten Only") become playable — these can be beneficial or detrimental.
The scenario describes a game mechanic where being bitten by a vampire or Dracula grants a player a "Bite token" and allows them to play specific event cards that are only available when they are under the effects of the bite.  These cards can have positive or negative consequences.