Electricity. What is it? Is it related to electrons? I thought it was? If the plug in my house is AC then why is one wire "hot" and one "neutral?" (on plugs in

Electricity. What is it? Is it related to electrons? I thought it was? If the plug in my house is AC then why is one wire "hot" and one "neutral?" (on plugs in North America at least) if there is a ground wire then why are plugs polarized? Why do some things come with a three prong plug and others don't?