What is an administrative proceeding?

A Department of Justice is an administrative agency. Whether all its proceedings are all administrative?

the DoJ doesn't have too many "administrative" proceedings. In general, the DoJ is the arm of the federal government that brings and defends lawsuits in federal court. I'm sure they have some "administrative" proceedings like hearings or bidding for procurement of supplies. And, because there are some things it does involving executive privilege/national security, the terms of the Administrative Procedure Act doesn't likely apply.

Administrative agencies are generally part of the executive branch of govt -- but have some quasi-legislative functions (meaning they can create rules) and some quasi-judicial functions (meaning they can have hearing and proceedings).

An administrative hearing (or proceeding) is one where your rights within that agency are addressed and resolved, without need to go to court. Example -- you apply for unemployment. There may be an administrative hearing to determine if you are eligible.

The DoJ is itself not primarily an administrative agency -- their primary function is investigation and enforcement, not administration.