Tree

 

AVL. A tree is balanced if and only if for every node the heights of its two sub-trees differ by at most 1.

B-tree is a generalization of a binary search tree in that more than two paths diverge from a single node.

In contrast to a B-tree, in a B+ tree, all records are stored at the leaf level of the tree; only keys are stored in interior nodes. The deletion of B-tree costs much than B+ tree.