B-Tree.

The Data Base server uses a B-Tree structure to organize index information
B-Tree has following type of index pages or nodes
1.Root node:-A root node contain node pointers to branch nodes which can be only one.

2.Branch nodes:-A branch nodes contains pointers to leaf node or other branch nodes
wich can be two or more.

3.Leaf nodes:-A leaf node contain index items and horizontal pointers to other leaf nodes
witch can be many.