-for actions taking place at or around the moment of speaking.Jackie is watching a film.
-for temporary situations.We are travelling around Europe this month.
-for fixed arrangements in the near future.I am meeting a friend at the shopping centre this afternoon.
-for currently changing and developing situations.The earth is getting warmer and warmer.
-with adverbs such as always to express anger or irritation at a repeated action.She is always complaining about everything.