Like in a conversation, an essay needs an appropriate closing. Instead of "goodbye," or "I'll talk to you later," though, an essay's closing or conclusion is more like a recap. It's a chance for you to remind your reader of the arguments you've made in your essay, and let them know that they are coming to the end.
The conclusion is where you recap your essay and create a closing for your reader. It's your opportunity to:
Think of your conclusion as a mirror version of your introduction, going from specific details that you have already discussed back to general details. Do not introduce any new ideas that were not previously identified in your essay in your conclusion.
(adapted from University of Arizona Global Campus, n.d.)