This uses the Venturi effect of a converging-diverging nozzle to convert the pressure energy of the motive fluid to velocity energy which creates a low pressure zone that draws in and entrains a suction fluid. After passing through the throat of the injector, the mixed fluid expands and the velocity is reduced which results in recompressing the mixed fluids by converting velocity energy back into pressure energy. The motive fluid is often steam but it can be a liquid or  gas. The entrained suction fluid may be a gas, a liquid, a slurry, or a dust-laden gas stream.