Balanced tree A tree where no leaf is much farther away from the root than any other leaf.
Different balancing schemes allow different definitions of "much farther" and different amounts of work to keep them balanced.
Height Balanced Tree aka AVL Tree (Inventors G.M. Adel’sonVel’skii and E.M. Landis), are selfbalancing binary search trees.
An AVL tree is one that requires heights of left and right children of every node to differ by at most ±1.
AVL Tree (Height Balanced Tree)  A tree whose subtrees differ in height by no more than one and the subtrees are heightbalanced, too.
An empty tree is heightbalanced.

Time Complexity 
Space Complexity 

Average 
Worst 
Worst 

Data Structure 
Access 
Search 
Insertion 
Deletion 
Access 
Search 
Insertion 
Deletion 

AVL Tree 
Θ(log(n))  Θ(log(n))  Θ(log(n))  Θ(log(n))  O(log(n))  O(log(n))  O(log(n))  O(log(n))  O(n) 