High-level gist is that it's not a direct popular vote. Instead, each state hosts a popular vote. The winner of that determines the winner of that state. Each state has a fixed number of electoral votes attached to it, based roughly (but not exactly) on population/size. If a candidate wins a state, they get that state's electoral votes. To win the election, you have to get 270 or more electoral votes.

There are some low-level details, like technically it's up to the states to decide whether they want to use the "winner takes all" approach to awarding their electoral votes. So there are some small and largely inconsequential exceptions to the above.