Of course, we use 'do' and 'does' in questions and negatives in the present simple.

• Does she like chocolate?
• I don't live here.

However, we can sometimes also use 'do' and 'does' in normal, positive sentences in the present simple. This is called using 'do' for emphasis.

We use it when we want to tell people that they are wrong!

• A: Jane doesn't live in Paris.
• B: That's not true. She does live in Paris.

We use it with imperatives. This makes them stronger but it's quite polite.

• Do sit down.
• Do have some cake!

We use it just to make the present simple stronger.

• I like coffee. (This is normal.)
• I do like coffee. (This means I really like coffee.)