Hi Gerard! I wouldn't say it was a stupid question. I believe the terms are a little cofusing, that's all.
A fuel injection system is a highly efficient way of metering the exact amount of fuel required to produce maximum power with maximum economy of fuel.
Some economy systems use single-point injection. A single injector, placed at the 'mouth' of the intake manifold, pulsing fuel as required by each cylinder. However, this does not produce optimum fuel atomization.
Multi-point injection is the answer. Some systems, such as the Rover Mini Cooper, use just two injectors, as the intake runners are siamesed for each pair of cylinders.
The ideal arrangement is one injector per cylinder. This allows accurate metering of the fuel, for each induction stroke of each cylinder.
Now, to answer your question. These injectors are placed in the intake port, just before the manifold to cylinder head joint. This allows the most direct injection into the cylinder, not obstructed by bends in the intake runner etc.
The manifold location also insulates the delicate injector from dissipated heat from the cylinder head. this is necessary to keep the fuel cool, and the injector functioning correctly. As far as I'm aware, the injector is never actually placed
directly in the combustion chamber, as this would destroy the delicate nozzle and hence the atomization of the fuel, which is how the fuel is introduced into the intake charge. If the fuel was allowed to puddle or flow as a liquid, the combustion process would be slow, and hence power production would be restricted.
I'm sorry if my description is confusing. I hope you can make some sense of my rambling!
Basically, direct injection and port injection - the same thing.
