I have a bunch of background systems that do various things.
I.e:
UnitManager : holds all the information regarding all the player units in the game
SaveSystem: self-explanatory
UnitActionSystem: handles all the actions a unit can
etc. etc.
What I've been using as my convention is.. a system is something the player directly interacts with. A manager is something that runs in the background and is triggered externally.
handler idk, service idk.
When you name things, what is the standard?