about AAA / RADIUS

can someone clearly differentiate AAA from RADIUS server?

are these both a protocol? I always see AAA associated with RADIUS or vice versa.

You probably know that AAA stands for Authentication, Authorization and Accounting. It is better described as an acronyms rather than a protocol on it's own.

RADIUS is a protocol, It offers AAA services. Other examples or AAA protocols are: TACACS and Diameter.

so RADIUS, TACACS, DIAMETER offer the same services for AAA? how does those 3 protocols differ then?