Actions on a regular basis — general facts, habits, preferences, abilities.
# I read three or four books every month.
# Kate speaks three foreign languages.
Actions that are happening now, at the moment of speaking.
# I'm reading a very interesting book now.
# Kate is speaking to her colleague now.
Verbs that express thoughts and feelings: like, love, hate, want, need, know, think, understand, remember, depend, prefer.
# A: Do you want to go out? B: No, not now.
# What are you saying? I don't understand you.