Scrypt is a recent key derivation function designed for password storage. It aims to improve on earlier similar functions such as PBKDF2 and bcrypt by requiring significant amounts of memory in addition to computation time.
Scrypt is a key derivation function that is designed to require significant processing time and memory. It is designed to improve on earlier KDF such as pbkdf2 and bcrypt by requiring more memory which is typically not a problem on typical servers and PCs but expensive on special-purpose ASIC that attackers may use to brute-force a KDF to crack password hashes. Scrypt is still recent and not widely used.