Explo(r|it)er.

Expertise, Experts, and the Expert Class

Distinguishing between expertise, experts, and the expert class.

Expertise

The actual knowledge, skill, and insight acquired through rigorous, domain-specific study and practice. Real and enduring.

ExpertA person who possesses expertise. (They may or may not be part of an institutional class).
Expert Class

The socially and institutionally recognized stratum of people who are labeled, credentialed, and given authority as "experts" in public discourse. This is a socio-political role, not just (or even necessarily) a function of real expertise.