Red Black Tree
In plain terms
A self-balancing BST using color rules to stay roughly balanced.
Going deeper
Red-black trees enforce coloring and structural rules to guarantee logarithmic height with fewer rotations than AVL trees. They're widely used in standard libraries.
Under the hood
Looser balance than AVL means faster inserts/deletes; backs many language map/set implementations.
Examples
Java TreeMap, C++ std::map, Linux kernel scheduler, ordered collections.
Think of it like...
Like a librarian who keeps shelves 'good enough' with minimal reshuffling rather than perfectly even.