what are irregular, action and linking verbs?

I can't understand

In contrast to regular verbs, irregular verbs are those verbs that fall outside the standard patterns of conjugation in the languages in which they occur.

Few instances of the same are pay-paid, lay-laid, etc.

 Action Verbs are actions in which a person or a thing might be involved. It is known as the main verb of the sentence. Instances of the same are: run, swim, read, fly etc. They can sometimes also express actions which one can't see such as 'think' or 'wish'. They can be time-telling verbs as well. They can tell when an action occurs- in present, past or future. It is a word belonging to the part of speech that is the centre of the predicate and which describes an act or activity.

Linking verbs , on the other hand, implies a state of being or condition for the subject, not an action. It links the subject to an equivalent word in the sentence.It may connect the subject with the noun. It is a verb that is used to connect a subject with an adjective or noun that describes or identifies the subject. The most common linking verb is be. Other common linking verbs are appear, become, feel, go, grow, look, remain, seem, smell, sound, taste, and turn.