the shiny balls on Christmas trees are ornaments
They are called a Bauble
balballs
The little balls are called sticky pads. They help them stick to trees and climb and stuff.
tinsel
lametta
the tree your thinking of is called the ever green plant such as the pine tree
tinsel
It's a Kousa Dogwood.
A tree with round spiky balls might be a Sweetgum tree. See the Related Link below for a picture of the Sweetgum tree.
walnut
There are 50 colored balls on the White House Christmas tree. Each ball represents a state.