Verbs are words that express actions or states of being. There are four main types of verbs: regular verbs which form the past tense by adding "ed"; irregular verbs which do not follow this pattern; transitive verbs whose actions pass to an object; and intransitive verbs whose actions do not pass to an object. Verbs can express physical actions, mental actions, or states of being. The most important verb that expresses a state of being is the verb "to be".