It stores versions of the document within the document itself via the INS and DEL elements.
Each date up at the top as various changes associated with it. On each day, changes were made to the document. By clicking show/hide you can toggle the changes from that day. By clicking Apply Changes, you can apply all changes up until that day (so if you're applying changes up till day 3, it will apply the changes from day 1 and 2 as well). Play Through Changes does the same thing, however it pauses for a second or two between the changes so you can visually see the changes (fade in/out of the elements).
Applying all changes will run through everything and give you the "final" version of the document.
I'll include a better explanation on the website itself, I was just tired as heck at 4am ;)
Each date up at the top as various changes associated with it. On each day, changes were made to the document. By clicking show/hide you can toggle the changes from that day. By clicking Apply Changes, you can apply all changes up until that day (so if you're applying changes up till day 3, it will apply the changes from day 1 and 2 as well). Play Through Changes does the same thing, however it pauses for a second or two between the changes so you can visually see the changes (fade in/out of the elements).
Applying all changes will run through everything and give you the "final" version of the document.
I'll include a better explanation on the website itself, I was just tired as heck at 4am ;)