Gamepasses are purchasable from the game-page, and vary in use as some may be cosmetic and others may give a competitive edge. There are currently four gamepasses that exist.

Paint Tool[]
The paint tool is a cosmetic gamepass that can be used to paint certain parts of your ship in different colours, there are up to 40 unique colours. It costs 50 Robux.
Night Vision[]
This gamepass was added to primarily help people early-game to collect moonstones on the dark-side of the Moon, however it can be used on the dark-side of any celestial body. It costs 200 Robux.
Donation[]
The gamepasse's name is self-explanatory, it's just a donation to encourage and help the development of SSE2. If you buy this gamepass it will give you a unique chat-tag. It costs 1000 Robux.
Summoning Staff[]
The summoning staff is a gamepass that unlike the others, can only be used inside of a private server. It is used to summon any sort of living entity (ex. Galieans, Leechs, European Squid.) It costs 400 Robux.