It’s a way to describe that one thing can cause another thing to happen and that from our perspective this doesn’t happen instantaneously.
Time exists in the same way that numbers do. It’s just a definition that allows us to tell things apart. Time and numbers don’t exist by themselves, but the definition will always be necessary to describe things that do exist.
Even the most simple description implies time and quantity. F.i. the sentence “apple is red” doesn’t mention the time or quantity directly, but the word “is” implies both time (present) and quantity (singular) and existence.
Saying only “red apple” doesn’t imply existence, so we can’t say that it describes anything that exists.
So the purpose of the human invention of the time concept is to describe existence. The meaning is dependant on what definition you use.