Spring RTS Engine

I see the word unitDefID alot on Lua call-in's and call-out's, often in the same context as unitID and teamID

every unit has a unitID, a unique number for each unit.
every unittype has a unitDefID, it is also a number and unique to that unittype

The same dichotomy applies to weapons;

A type or class of weapon, (or a weapon definition; hence weaponDefID) vs. an individual instance of that weapon on an individual unit.

Lassie is a unitID
Dog is a unitDefID