Present Simple: Mainly used for facts, habits and truths.
She is afraid of the dark. Dolphins can swim - facts
Unicorns don't exist - truths
I cycle to school every day - I clean my teeth twice a day - habits
Present continuous: When we are talking about activites, temporary situations and things that are happening around now - (and future arrangements). The boys are carrying a big suitcase. (verb to be + verb+ing)
The twins are wearing identical clothes. - events happening now