The present perfect tense is used to describe actions that began in the past and continue in the present, actions that have occurred multiple times up until now, and completed past actions that have present relevance. It is formed using the present tense of the auxiliary verb "have" plus the past participle of the main verb. Examples are given of affirmative, negative, and interrogative sentences using the present perfect tense structure and common time expressions used with it like "ever", "never", and "since".