Verbs are 'doing' words, they tell us the action being performed. Verbs are the words that change tense.
I walked to the library. - past tense.
I am walking to the library/I walk to the library. - present tense
I am going to walk to the library. - future tense
They were dancing to the music - past tense
They are dancing to the music - present tense
They are going to dance to the music - future tense