It is quite new indeed, see the meta Meta:
From the latter, quoting waffles:
As it stands (and this is all subject to change until the feature is formally announced):
Who can suggest an edit?
- Users with 2k rep can make edits at will without needing to "suggest" them of, course!
- Registered users can suggest an edit to any post
- Anonymous users can suggest edits to any post more than 1 day old
Where do suggested edits go?
Suggested edits are held in a peer review queue of a fixed size. If the queue fills up, no more edit suggestions will be allowed until the queue has some empty space.
How do suggested edits get approved?
Our goal is
- Have two reviewers look at each edit in the ideal case to ensure quality of edit.
- Ensure that many reviewers are participating in the process and all edits are not being approved or rejected by a single reviewer.
Again, this is all subject to change. Wait for the official announcement on the blog.
Edit 7 Feb 2011: et voilà, Suggested Edits and Edit Review.