What is the difference of linking verb and action word?

A linking verb has a complement which describes the subject; an action verb has a complement which is acted on by the verb.

For instance: in "he feels the ball" the ball is acted upon by the verb and does not describe "he", but in "he feels cold", the Word cold describes "he". The questions are "WHAT did he feel?" for actions and "HOW did he feel?" for linking verbs.

(Note: if the complement is included you might get "how" for action verbs, as in "how did he feel the ball?)