Agression is betting and raising more than checking and calling during a hand.
Bluffing is betting with a worse hand with the intention of getting your opponent to fold a better hand.
Bluffing is an aggressive move but it is not "aggression"
Also aggression has nothing to do with how many hands you play. The number of hands you play makes you either tight or loose. That is why players are described as Tight Aggressive, or Loose passive. The descriptions indicate how many hands they are likely to play and how they will act post flop.
I hope this helps.