Boosters increase various rates on the server. They can either be activated Globally for everyone or be activated Personally for a specific player. At present, there are 4 boosters available on PokeMC 

Boosters Available:

Catch Booster - Doubles the Catch Rate of Pokemon for 30 mins
Boss Booster - Doubles the chance of encountering a Boss for 30 mins
Shiny Booster - Doubles the shiny catch rate for 30 mins
Exp Booster - Doubles the amount of Exp your Pokemon gain for 30 mins

• Through prizes from Events.

• As rewards from the Season Journey.

• Purchase from the Webstore (Global only)

• Boosters automatically activate when you get them, either from in game activities or from the webstore

• Boosters stack in time. So acquiring multiple boosters will extend the boosted period. (rates do not stack)

• by using the command /boosters check [username]

• This will bring up a summary of boosters that have been applied to you either globally or personally

• You will also receive a message in chat when a booster runs out.