What is a hash collision and how can it be handled?

A hash collision occurs when two different keys produce the same hash value, mapping to the same index in the hash table. Common handling methods are: Chaining (storing collided elements in a linked list at that index), Open Addressing with Linear Probing (finding next empty slot), Quadratic Probing (using quadratic function to find slots), and Double Hashing (using second hash function). Good hash functions minimize collisions.