Ok, this is only a sample tree. You can choose from up to 8 or 9 "classes" per main class. For Instance I am a Cleric as a main class. Under that my tree talents are broken up into 3 of the 8 available. Each has their own unique abilities and attributes. I could be a healing tank, a dpsing healer, a ranged healer, a anti-healer healer....tons of options.
And...there is a unique PVP tree on top of all of that... AWESOME!!!!!