What is the difference between NIST 800-171 and NIST 800-53?

More context

The practical audience split: 800-53 applies when you operate a federal system or seek FedRAMP authorization; 800-171 applies when you are a defense or civilian-agency contractor storing or processing CUI on your own infrastructure. NIST 800-171 is also the technical foundation of the CMMC program for the US defense industrial base.

Because 800-171 requirements are tailored from 800-53, evidence collected for one substantially supports the other. Configuration-focused families (access control, audit and accountability, configuration management, identification and authentication, system and communications protection) are where CIS benchmark scanning produces the bulk of the technical evidence for both documents.