warningsign Do-emphasis

Do can be used in affirmative sentences to emphasise or contrast something. 

E.g.

-John doesn't like pizza - Yes he does like pizza!- A John no le gusta la pizza- ¡Sí que le gusta!

I do like to listen to jazz when I study- me gusta escuchar jazz cuando estudio

I don't speak with him anymore, but I do see him occasionally- No hablo con él, pero sí lo veo ocasionalmente