The Pluggable Authentication Module (PAM) is a flexible framework used in computer systems to manage authentication tasks. It allows system administrators to integrate various authentication methods, such as passwords, biometrics, or smart cards, without changing the underlying application code. This modular approach simplifies the process of adding or modifying authentication methods. PAM works by providing a set of APIs that applications can use to authenticate users. Each authentication method is implemented as a separate module, which can be easily plugged in or removed. This design enhances security and adaptability, making it easier to meet different security requirements across systems and applications.