A verb is "a word or phrase that describes an action, condition or experience" (Cambridge University Press, n.d., para. 1). For example, in the previous sentence, "is" and "describes" are both verbs.
See Verbs for more in-depth information.
Reference
Cambridge University Press. (n.d.). Sentence. Cambridge dictionary. Retrieved February 24, 2021, from https://dictionary.cambridge.org/dictionary/english/sentence