One of the ways that the community moderates the site is by reviewing posts that have been identified by users or the system as needing review to help determine whether the contribution is beneficial to the site. Once you have achieved 500 reputation, you have access to the first set of review queues – and you’ll gain access to more as your reputation increases.
Review queues show you posts one at a time so that you can evaluate what, if any, action is needed. Each queue is equipped with distinct options so that you may take appropriate action. In one queue, you may be looking at the first posts by new users. In another, you may be reviewing edits suggested by lower-reputation users or assessing questions to determine if they should be closed or reopened.
Each queue has a specific purpose, and each of the following Help Center pages will help you learn more about how to perform reviews in each queue:
Close votes – 3,000 reputation. When questions aren’t a good fit for our format or scope, they need to be closed. Questions with active close votes or close flags show up in this queue so that others can review whether they should be closed.
Reopen votes – 3,000 reputation. When closed questions get edited, or if others disagree with the closure, they can be reopened. Questions with active reopen votes, as well as questions whose bodies have been edited during the first 70 days since they were closed, appear in this queue.
Low quality posts – 2,000 reputation. This queue contains posts that were determined to be of low quality based on a system-generated quality score and/or user flags.
Suggested edits – 2,000 reputation. Directly editing other people's posts requires 2,000 reputation. When users without enough reputation submit an edit, their proposed changes go into this queue for approval before they are applied to the post.
First answers – 500 reputation. The goal of this queue is to help users who may be unfamiliar with the site. This queue specifically handles the first few answers submitted by a user.
First questions – 500 reputation. The goal of this queue is to help users who may be unfamiliar with the site. This queue specifically handles the first few questions submitted by a user.
Late answers – 500 reputation. This queue contains answers that were posted much later than the question. Reviewing these posts makes sure that great new answers get seen and problematic answers get removed.
Triage (only on Stack Overflow and a few other sites) – 500 reputation. The primary goal of Triage is to quickly sort questions into groups: good as is, needs community editing, or should be closed/flagged.
(Note: The First questions, First answers, and Late answers queues do not exist on Meta sites.)
See also this FAQ on Meta Stack Exchange for more info about the review queues.