Password Salting is a technique used to help protect passwords stored in a database from being reverse-engineered by hackers who might breach the environment. Password salting involves adding a string of between 32 or more characters to a password and then hashing it. Password salting is one of the most secure ways to protect passwords stored for future authentication without exposing them should your website be breached in the future. However, salted passwords must also be iteratively hashed multiple times for this protection to work. When salting and recursive hashing are employed, Rainbow Tables become useless for password cracking.
Source: Techopedia
Additional Readings:
How to Secure Your Website against Data Breaches
Related Terms: Hashing, Rainbow Tables