Since a hash function gets us a small number for a key which is a big integer or string, there is a possibility that two keys result in the same value. The situation where a newly inserted key maps to an already occupied slot in the hash table is called collision and must be handled using some collision handling technique.
Hashing Set 2 (Separate Chaining): https://www.geeksforgeeks.org/hashing-set-2-separate-chaining/