Frenzy is a keyword ability.
If the creature with frenzy is not blocked, it gains +X/+0 until the end of the turn.
- 502.66a Frenzy is a triggered ability. “Frenzy N” means “Whenever this creature attacks and isn’t blocked, it gets +N/+0 until end of turn.”
- 502.66b If a creature has multiple instances of frenzy, each triggers separately.