The Offline Files feature is in the control panel...
The tab is pretty self explanatory. It enables you to keep copies of your network files on your PC for you to work with "offline" ergo the name. It allows you to sync up with the network versions as well..
The disk usage tab shows your disk usage (duuh). It lets you manipulate/delete the offline files cache...
There's a tab for encrypting these files (optional)..
It allows you to check for a really slow connection and it will modify the way you work based on the status of that check.