A password hash is a scrambled, fixed-length representation of a password created by a mathematical algorithm. Instead of storing the actual password, systems store its hash, making it much harder for attackers to retrieve the original password if the data is stolen. Hashing is a one-way process, meaning you cannot easily convert a hash back to the original password. However, some weak hashes can be cracked using special tools or techniques, so strong algorithms and additional protections are important for security.