If something is ancient (ain shint), it’s really old. We use this adjective for civilizations, buildings, machines, and sometimes we use it for people who are still living.
Ancient civilizations built many interesting things out of stones and rocks.
The ancient city of Damascus has been inhabited for thousands and thousands of years. (inhabit = to have people living there)
Raheema’s biology teacher is ancient. He’s been teaching since 1972. (The use of the word "ancient" to describe a person is a good example of an exaggeration. See the note below.)
My Toyota is a 1993 Previa. It’s ancient, but I still like to drive it.
Cell phone technology is changing so quickly now, a phone that’s just a few years old already looks and feels ancient.
Americans are fascinated by the ruins of ancient civilizations because as a country, the United States is not very old.
Note: It’s fairly common for people to exaggerate when they describe something. I don’t know how common this is in other languages, but it happens often in English. We know that a person, a car, or a cell phone is not really ancient, but the choice of this word helps to express the feeling that someone or something is really, really old.