How do collisions happen during hashing?
Usually the key space is much larger than the address space, thus, many keys are mapped to the same address. Assume that two keys K1 and K2 map to the similar address. When the record with key K1 is entered, it is inserted at the hashed address, but when another record with key K2 is entered, it is a dilemma where to put in as a record with key K1 is already there. This situation is known as a hash collision.