A MIDI controller doesn't produce sounds on it's own - it needs to be connected to a computer running a software instrument/VSTi. It usually is, but doesn't have to be, a keyboard. It may provide have other things like knobs and pads that can be mapped to functions in the VSTi or DAW.
When I think of an electronic keyboard, it's a thing with a keyboard that has it's own sound generator. It may or not have a MIDI interface or be able to connect to a computer.
Hope that helps.
J