First and foremost, FamilySearch.org is vast collection of digitized historical records with millions of new records being added every week.
The complete collection of all the books and documents in the FamilySearch Libraries around the world in contained in Catalog. All of the microfilm images collected from all over the world since 1938 are also listed.
There is a pull-down menu (where the word "Any" appears) that will indicate which library of the FamilySearch system has the resource.
There is a section called Genealogies, that contains several valuable resources: The Ancestral File (AF), The Pedigree Resource file (PRF), the International Genealogical Index (IGI), and the Community Trees files. Here is a screenshot:
In addition, FamilySearch.org has a huge collection of digitized books. The last number I heard about the collection was that it was over 250,000. There was also a recent notice that they were adding collections from 32 State libraries around the United States.
The Memories section contains millions of photographs, documents and stories.
If you would like to explore the FamilySearch.org website, I suggest starting with the links in The Family History Guide. This is one of the FamilySearch Apps and will give you a good outline of the resources in FamilySearch.org as well as a very good introduction to family history in general.