Right rotation

Right rotation refers to the following:

In an array, moving all items to the next higher location. The last item is moved to the first location, which has been vacated.
In a list, removing the tail and inserting it at the head.
In machine code moving all bits in a register to the right, with the rightmost becoming the leftmost.

Tree rotation

In a binary search tree, a right rotation is the movement of a node, X, down to the right. This rotation assumes that X has a left child. X's left child, R, becomes X's parent node and R's right child becomes X's new left child. This rotation is done to balance the tree; specifically when the left subtree of node X has a significantly greater height than its right subtree.
Right rotations are order preserving in a binary search tree; it preserves the binary search tree property. AVL trees and red–black trees are two examples of binary search trees that use a right rotation.
A single right rotation is done in O time but is often integrated within the node insertion and deletion of binary search trees. The rotations are done to keep the cost of other methods and tree height at a minimum.