Most Helpful Guy
A season is what the UK calls a series. A series here is the entire run of the show.
Scripted shows have one season per year. Major shows are "fall season" shows that get about 22 episodes per season. The summer season is the short season, for shows that don't get as many episodes.
So, Friends is a series that ran for 10 seasons and 10 years.
Reality shows, on the other hand, can have more than one season per year, which is more like the UK. But we still call them seasons.