B-tree

In computer science, a B-tree is a self-balancing tree data structure that maintains sorted data and allows searches, sequential access, insertions, and deletions in logarithmic time. The B-tree generalizes the binary search tree, allowing nodes to have more than two children.

B-tree of order 3

B-tree in which each node contains only keys (not key–value pairs), and to which an additional level is added at the bottom with linked leaves

B-tree of order 4

tree data structure similar to B+ trees