WordPress has built in feature that automatically saves versions or revisions of your posts as you edit and create them. WordPress, by default, will save copies of each edit made to a post or page, allowing the possibility of reverting to a previous version of that post or page. The saving of revisions can be disabled, or a maximum number of revisions per post or page can be specified.
Post revisions are stored in your “wp_posts” table in your MySQL database.
This handy feature allows you to go back to a certain post revision and restore that revision, thus taking the post content back to previous date in time.
There is a cost to having all these saved revisions of your posts in the aspect of database entries. Instead of having a single MySQL database record for your post you will have multiple records for each post therefore increasing the total amount of records and an increase to the total MySQL database.This in total could slow down the overall page loading speed of your WordPress blog.
To totally disable the post revisions you can do this by adding a constant to you WordPress wp-config.php file which is located in the root of your WordPress installation. WP_POST_REVISIONS are enabled by default. We advised this to do at the initial setup. You can add the following to wp-config.php after your site been online for sometime, but you’ll need to remove post revisions in your database, we explain that in another post
define('WP_POST_REVISIONS', false );
You also the ability to set a maximum number of post revisions that you want to use for each post.