1_ Refers to future. ( An action in future which is already planned )
🔴We are going on holiday next week.
🔵I am leaving Iran to Italy tomorrow.
2_ An action which is going on at the moment. ( An action that is going on during this period of time or a trend )
🔴You are studying English grammar.
🔵More and more people are becoming vegetarian.
3_ Describe a temporary even or situation.
🔴Weather forecast was good, but it's snowing right now.
🔵He usually plays with computer, but he's playing with his phone tonight.
4_ Describe or emphasize a continuing series of repeated actions by using “always, forever, constantly". ( Emphasize the annoyance of the action )
🔴You are always leaving your shoes on the carpet.
🔵You are constantly complaining about your mother-in-law.