The present simple (also called the simple present) is used for actions that are repeated or habitual: I get up at 7 o'clock.
The present continuous (also called the present progressive) is used for actions that are unfinished at the moment: I am writing to you at the moment.
We also use the present simple for states that are permanent: I live in London.
We use the present continuous for states that are temporary: I'm living with my sister while my house is being decorated.
I hope this helps.