1 For an action happening at the time of speaking.
It is raining outside.
I’m not wearing a coat as it is not cold.
Why are you sitting at my desk?
What’s the baby doing?
He’s tearing a 5 pound note.
2 For an action happening about this time but not necessarily at the moment of speaking.
I’m reading a play by Shaw.
He’s teaching French and learning Greek.
3 For a definite arrangement in the near future, the most usual way of expressing one’s plans.
I’m meeting Peter tonight. He’s taking me to the theatre.
What are you doing tomorrow afternoon?
Yes, I’m playing Tennis with Anne.
Note: The time of action must always be mentioned as there will be confusion between the present and future meaning. The verbs “come” and “go”, however, can be used without any time expression.
Then Verbs of perception.