Sales person.

Yes. We do it using computers now, so a lot of what I do is more database management but the basic method we use for accounting has been around since before the year of our lord 1300. All the stuff we do is just to make it possible to do at scale.

Im a process auditor, so they would probably understand but would think my job is not necessary ( can't blame)

Yes. I'd just say "you know how the Courts have the power to do X, and decide Y? Well the government decided to devolve those powers to an independent office, so that people didn't have to pay for lawyers and deal with complicated legal processes. I work in that office making the Y decisions."

I wonder how weird they would find: I work for one company. Other companies pay that company for me and my coworkers to do work for them. I may be moved to different companies to do similar type of work at each company.