802.1X is a standard that enables the use of an AAA server in a domain environment by providing port-based network access control. 802.1X authenticates users or devices before granting them access to the network resources, and can also authorize them based on their roles or policies. 802.1X can work with different AAA protocols, such as RADIUS or TACACS+, to communicate with the AAA server.
Reference:
CompTIA Network+ N10-008 Certification Study Guide, page 211
CompTIA Network+ N10-008 Cert Guide, Deluxe Edition, page 382
Configuring AAA Services - Cisco3