Any English tense consists of a few components: verb, doer or subject, time etc.
A verb expresses an action or a state.
Action verb (dynamic verb)
Action verbs express physical or mental action. They describe processes that entail change over time.
I go (physical action, that entails a movement of a leg, a change in location of a person)
I think (mental action entails different stages of a thinking process)
Stative verb (State verb)
Stative verbs describe a state of being, in contrast to a dynamic verbs, which are actions. They describe situations that are static, i.e. unchanging throughout their entire duration. That’s why they are not a process.
I know / like / understand