Binary tree :- Any tree with max two child nodes
Full Binary tree:- Any tree with a given level h having 2^h-1 elements
complete binary tree : if we start removing elements from full binary tree ( 0 or more from rightmost leaf node )result will always be a CBT
almost CBT : it is a complete binary tree in which last level is not full (i.e at least one element has to be removed from full binary tree)
BST is based on values values in left are less than root and values at right are more than root
e.g
30
12 45
for balanced BST refer
https://www.cpp.edu/~ftang/courses/CS241/notes/self%20balance%20bst.htm