What are a memorized secret and a password?

A memorized secret is a knowledge-based authentication means where the subject authenticates by entering a secret only it knows, such as a password, PIN or security question; a password is a confidential character string agreed between subject and verifier at registration and used afterwards to authenticate.

Memorized secrets need enough complexity and randomness to resist guessing, phishing and brute force; password policies (length, character mix, expiry, reuse) determine their strength.

Go deeper:

• Password (Wikipedia) — cracking, policies and what actually makes a password system secure.
• NIST SP 800-63B-4 Authentication and Authenticator Management — every authenticator type defined and graded by assurance level.