Hey there, I just wanted to know if somebody could tell me what are boons in this game?

Boons are the community bonuses you get for completing a legacy. For example, when you start a new community and choose the builder boon, you'll have free power & water. Since the four boons make the game easier (especially the warlord boon giving you tons of grenades and ammo), the leaderboards are divided between runs with them and runs without them.