"Family Tree will enable you to:
- "Save family information into a genealogy tree
- Easily submit the names of ancestors for temple work
- Edit and delete incorrect data, including relationships
- Connect and collaborate with others on shared family lines
- Show where information came from. You can even link to online photos and documents"
You also may want to view a rather nice video, Introduction to Family Tree, available at http://goo.gl/v9xA1. I was especially interested in the comments saying that you will be able to link your online data to online sites (presumably both inside and outside of FamilySearch.org) to serve as source citations to provide verification of your records.