What does AAA stand for and what does each component do?

Authentication (who are you?), Authorization (what can you do?), and Accounting (what did you do?).

AAA = Authentication, Authorization, and Accounting

* Each user passes through three gates: prove identity, get permitted actions, then have actions logged. *

• Authentication - "Who are you?" - Controls who is permitted to access the network

• Authorization - "What can you do?" - Determines what actions users can perform while accessing the network

• Accounting - "What did you do?" - Makes a record of what users did while on the network

Analogy: Like a credit card - identifies who can use it, how much they can spend, and tracks what they bought.

Go deeper:

• AAA (computer security) — Wikipedia — the framework and the protocols (RADIUS, TACACS+, Diameter) that implement it.