Question

what is a turbine....?

Answer 1

A turbine is a machine that transforms rotational energy from a fluid that is picked up by a rotor system into usable work or energy. Turbines achieve this either through mechanical gearing or electromagnetic induction to produce electricity. 

Answer 2

The device that converts linear mechanical energy to rotational mechanical energy(eg. flowing river water to a rotating rod or whatever) and supplies it to a generator to convert it to electrical energy