The document discusses verb movement in syntax. It explains that in English, auxiliary verbs like "have" and "be" can appear in the tense slot of a sentence unless that slot is filled by another verb, whereas main verbs like "eat" appear in the verb phrase. Some languages exhibit verb movement where all verbs, not just auxiliaries, appear in the tense slot. This movement of verbs can be analyzed as the verb adjoining to the tense feature in a higher clause.