Edits suggested by users without the full edit privileges (<2k for questions and answers; and <20k for tag wikis)
Users with 2k reputation have the privilege to edit any question or answer.
Users who have not reached the level of 2k reputation are allowed to suggest edits. These are not applied immediately, but go into a queue where users who have edit privileges can vote to approve or reject them.
If the edit gets approved, there is a 2 reputation bonus for the user who made the suggestion. If the edit is rejected, a reason will be displayed on the suggested edit page. One can track suggested edits under the suggestions section of the activity tab on the account profile.
The suggested edits feature also applies to users who don't have 20k reputation to suggest edits to tag wikis.
Reference: adapted excerpt and wiki from the main Meta SE site.