All this about AC is confusing. First let's think about what a current is.
Electric current is a flow of charge.
Charge is the stuff you get when you rub a balloon against your jumper, or when you go on an escalator in a hot dry shop. Lots of people just call this 'static'. It happens when some electrons are rubbed out of one material into another. The one that loses electrons becomes positively charged. The one that gains them becomes negatively charged.