Comment by Symmetry

They just throw stuff out the back of the rocket really fast to move forward, like any other sort of rocket. The nice thing about electrical rockets is that they decouple the energy used to throw the propellant from the chemical energy generated from burning the fuel, so you can end up throwing it out fast for very efficient rockets if you have enough electricity.

http://hopefullyintersting.blogspot.com/2015/03/rockets-elec...