“Tomorrow is the most important thing in life. Comes into us at midnight very clean. It’s perfect when it arrives and it puts itself in our hands. It hopes we’ve learned something from yesterday.” - John Wayne

Perfect - A verb form expressing action completed prior to a fixed point of reference in time.

Tense - A set of forms indicating a particular time.

Perfect tense is sometimes referred to as “perfective aspect”. Perfect tense talks about an action that occurs at one time but is seen in relation to another time. In speech perfect tense usually comes up while talking about something you did: I saved the book for you. Saving the book was in the past but it is ready for you now. I have read a lot of books. I read the books in the past but they are part of me in the present.

You can get a detailed explanation of Perfect Tenses here.

Basically, perfect tense is when two states of time are being discussed against each other even if one of those states is inferred (usually the present). Don’t confuse perfect tense with the simple past tense which is only discussing actions that already happened. The simple past tense is much more common than perfect tense.