Cold air intake is basically a system for placing the air filter outside of the engine bay where it will get "cold" air as opposed to the hot air from around the engine.
Fuel injection is just that. Fuel is injected into the cylinder where it mixes with the air, as opposed to a carbuerator that mixes the air and fuel before it enters the cylinder.
you might be thinking of CAI = cold air induction. and mixing it with fuel injection.
CAI is getting the air into the engine for combustion, fuel injection is adding the fuel to the air coming in, add a spark and boom...down goes the piston....lol