Tree
A tree is used to represent a hierarchical tree structure with a set of connected nodes. Each node in the tree can be connected to many children (depending on the type of tree), but must be connected to exactly one parent, except for the root node, which has no parent. wiki)
Classification
Binary Tree
Complete Binary Tree
Perfect Binary Tree
Balanced Tree (B-Tree)
Binary Search Tree
AVL Tree
Red Black Tree
B+ Tree
MySQL