A recent feature committed into Guvnor trunk is the ability to track what you have opened, or edited - this shows up under an "Inbox" item in the main navigator.
Clicking on the recently opened item will open a listing of all items you have "recently" opened (it tracks a few hundred items that you were last to look at). Pretty simple
Any items that you save changes to, or comment on will show up here, once again, pretty simple
This tracks changes made by *other people* to items that are in *your* "Recently Edited" list. When you open these items they then are removed from this list (but remain in your Recently Edited list).
All pretty simple (one of those things that are simple to grasp and use, and painful to implement ! as are all the good things in life).