Importing session data in Pro Tools is quite valuable as a time saver. It also serves as the best way to keep continuity on song to song when working on a project or album. As the name suggests, it allows you to pull in data from one session into another. This can be audio/midi or this can be settings such as plugins, routing, pan, volume, etc. The exact method and process will depend on what you are after for your end results.
In this Free Tutorial video Kris shows us a very useful but often overlooked routing technique to use a reference track in your Pro Tools mix session.
In this Video overview Steve shows us the new Models, Mic's and Cab's of the Avid Eleven MKII plugin and its most useful feature the accompanying Cabinet Plug-in and its routing capabilities to allow you run multiple different cabinets from one instance of Eleven MKII to get the perfect tone blend.
In this Video Neil shows how incredibly useful "Track Presets" can be for using multi channel Virtual Instruments with Pro Tools as well as for simpler tasks such as effects channels.