Dumb question #5634129851 - What's a coilover?
Yep, a coil over a strut - but they are built as one unit and work together. Quite often cars will have a Macpherson strut setup, where the spring sits over the strut, but both parts are changeable independently, whereas with a coilover you have to change the whole unit.
However, coilovers tend to give a lot greater adjustability, better damping, improved control, etc etc.