Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having replaced carburetors during the 1980s and 1990s. A variety of injection systems have existed since the earliest usage of the internal combustion engine.

It is a way of providing fuel to an engine. It has been around a LONG time (mechanical fuel injection in particular) and in an electronic fuel injection system, simply uses a solenoid of some type (an injector) to start and stop the flow of fuel into the engine vian an engine management system. Injectors have been used anywhere from pre-throttle blades, into the actual combustion chamber.

Bunch of electronically controlled squirt guns that spray fuel into the intake system of an engine.

It is just what it says it is. A system that takes fuel & injects it in the cylinder.

It replaced carburettors over 10years ago to deliver fuel in an engine.