Revisions are enabled by default on development sites, which means that each site keeps track of each change that is made by each user, per page. This can help issues when content is mistakenly deleted, and an earlier point can be reverted. Each update to a page is tracked as a separate revision and can be labeled.
Revisions allow all Editors and UICs to keep track of the changes made and can be especially helpful if multiple people are making changes to the same site.
