A binary tree is a rooted tree in which every node has at most two children.
A full binary tree is a tree which every node has zero or two children.
A perfect binary tree is a complete binary tree in which leaves (vertices with zero children) are at the same depth (distance from the root, also called height). It has
Sometimes the perfect binary tree is called the complete binary tree. Some others define a complete binary tree to be a full binary tree in which all leaves are at depth n or n-1 for some n.