If you want to turn off revisions or autosaves see my article
WordPress – How to Turn Off Auto Save and Revisions
If you are writing or editing a post for more then 60 seconds WordPress will automaicly create an autosave record in the posts table of your WordPress database. This record will continue to overwrite every 60 seconds so dont be worried that your database will grow out of control while you are creating or editing posts. If you ever find yourself writing a post and either your browser or your computer crashes you will have at a minimum all of your work but have lost the last 60 seconds.
In the WordPress database in the table posts the post_type will be revision and the post_name will be [post ID]-autosave. So if the post ID is 5 the format will look like 5-autosave.
When a post is created and published it will create the post and it will also creat a revision at the same time. Each time an article is edited and saved it will add an additional record to the the table posts. So by the first saved edit there is at least 3 revisions that exist in the database and if you wait long enough to save your data it could create the autosave record and you will have 4 records for one post.
The revision posts are in the post table as well and the post-type will be revision and the post-name will be [post ID]-revision. So if the post ID is 5 the format will look like 5-revision. On the very first saved edit the format will change for the post name a revision number will be appended so the new format will look like [post ID]-revision-[revision number] so if the post ID is 5 and this is the first edit it will look like 5-revision-2 and on the second edit a new record will be created with the the post_name of 5-revision-3.
A really good reference for how the tables will look is on a post called