Mod Note: One post has been edited to remove personally-identifying information.
FamilySearch is the program where we build our Family Tree. If you sign into FamilySearch for the first time, you will need to add the living individuals, (yourself, parents, and perhaps grandparents), until you get to the first deceased person in each line. After that you will be able to see all your ancestors already listed in Family Tree.
We hope this clarifies the difference.
Please let us know if you need additional help.
I would (urgently) modify @Sanra's blanket statement to read "After that, you may be able to see all of your ancestors already listed in Family Tree". If you have lots of cousins who contribute to FamilySearch's tree, then most of your deceased relatives probably are here, but if you're the only one in your family who does genealogy, then you're probably going to have to enter most of your relatives.
For example, the only direct ancestor of mine who was already entered here was one great-grandfather, whose baptism was mis-indexed as female, so somebody dutifully replicated the index's nonsense in one of FamilySearch's prior systems.