Can someone explain the difference between membrane, scissor and mechanical keyboards? I have no idea what my preference would be. Let alone what kind of keyboa

Can someone explain the difference between membrane, scissor and mechanical keyboards? I have no idea what my preference would be. Let alone what kind of keyboard I'm currently using (which is the best I one ever owned). I'm also surprised why no-one seems to take travel into account. I find that I type more relaxed (and faster) on keyboards with flat keys that don't travel much.