Benefits of Peer Review

There are several benefits to participating in a peer review. When you participate in a peer review, you are putting yourself in a position to both learn and teach. There's an adage that says you're never too old to learn and never too young to teach, and I find that to be quite apt when thinking about the benefits of a peer review. The end result is that your essay skills improve, as do those of your classmates.
Your skills improve with the insight you get from your classmates. A peer review might typically have 3-4 peers reviewing your work, and maybe not all of them will have useful insight, but someone will. So you learn how to receive criticism in the sense that you learn how to filter it for the valuable insight and actionable tips. Learning how to filter criticism is a powerful thing in life.
Furthermore, when there is useful insight from your peers, and you work with that, this means you are getting better. Your skills improve when you learn things from others. It is very difficult to be an island, and just learn everything yourself. At the worst, your peers will help with superficial things like spelling, but at best they will break down your preconceptions, having you challenging your assumptions, and showing you entirely new ways of thinking.
When you review the works of your peers, you also benefit. First, you get those same things above, learning new ways of thinking, and gaining insight into how others see the world. If you are reviewing an essay that you also wrote about, you will see how other people perceive the exact same question or problem. You will see entirely different ways to solve a problem from the way you did; and these ways might be just as correct. It is an important lesson to learn that there are many different ways to conceptualize a question or challenge, and it is valuable to gain insight as to how others go about resolving an issue.
Another means by which you benefit from participating in the peer review process is that you sharpen your skills at evaluating the work of others. At first you might do it poorly, and just compare the other person's work to your own, but over time you will learn how to evaluate the quality of others' work by thinking carefully about it. Why did they say that? Why did they think that? Is that a good approach or are there mistakes in there? When you start thinking critically about the work of others, you are not only developing your critical thinking skills in a way that will help you later on in life, but you are also putting yourself in the position of learning new approaches.
Further, peer review sharpens all the students. If you participate in peer review and take the process seriously, you will end up making yourself better, and your peers better. When you make your peers better, they in turn will be able to make you better when they review your work. So peer review is a means by which people improve as a group, over time.
There are definitely some downsides to peer review. There has to be a guided process so that it is not simply the blind leading the blind, for example. Students who do not take the exercise seriously, or review without empathy and just deliver harsh criticism, can render the process of no value, or even negative value, but overall, there are a lot of benefits that come from peer review of essays. The best way to ensure that you receive these benefits is that you understand what benefits you are trying to get – if you approach peer review with the knowledge that you want to make your own essays better, and want to understand different perspectives and approaches, then you will be in a great position to learn about critical thinking and apply those skills to the task. Taking this approach will allow the peer review system to excel and for you to get the most out of peer review.