In direct injection the fuel is injected INSIDE the cylinder,
In indirect injection it's injected in a small chamber adjacent to the cylinder used to create turbulence that will help mix the air with the fuel. (This is old technology, nowadays all diesels are direct injection.
That's for diesels. In petrol engines the injector pumps the fuel in the air intake conduct.
Haven't seen any carburetor in a Diesel engine, ever.