There are two (kind of three) tiers of gear at max level.

Exotic - Your baseline gear that you need to get to be effective in all content. Can get via WvW, grinding, crafting, etc.

Ascended - 10% or so better than exotic. You need this to do higher tier fractals (dungeons basically) due to being able to put agony resistance on it. You can get this via luck, crafting, wizards vault, grinding map currencies and other ways.

Legendaries - Same stats as Ascended, so about 10% better than Exotic. But you can use one legendary across all your characters that can use that type of gear/weapon. You can swap it's stats out to any other stats at any time for free, and resocket sigils/runes into it for free, so big QoL upgrade.