Conclusions usually

• Restate/rephrase the thesis statement 
  
• Reviews the main points of development and how they speak to/argue for the thesis
• Refer back to an idea, issue, or concern started in the introduction
  
• For argumentative essays, include an emotional appeal and/or call to action, with which the writer (explicitly or implicitly) connects the “logic” of the argument to a more passionate reason intended to sway the reader
• For informative essays, include something memorable (a quote, statistic, something to think about, etc.) to leave the reader with in relation to the offered information
  

Ideally, a conclusion will work in tandem with an introduction, having some kind of “call back” element to remind your reader of the powerful opening you provided. Additional advice for conclusions is found in the following video.