X uses components working together:
Supplicant. This is your device. It runs software that responds to authentication challenges. Windows, macOS, and Linux have built-in supplicants. So do most mobile devices.
Authenticator. This is the network device you connect to: switch or wireless access point. It acts as a gatekeeper, enforcing the block until authentication succeeds.
Authentication server. This is typically a RADIUS server. It validates credentials and tells the authenticator whether to grant access.