The appraiser and umpire roles are related, but they are not the same assignment.
An appraiser develops an independent position on the disputed amount of loss. That may involve reviewing estimates, photos, reports, measurements, and site conditions to understand the scope, pricing, and valuation disagreement.
An umpire is typically used when the two appraisers cannot agree. The umpire reviews the competing positions and helps the appraisal panel move toward a reasoned award.
A file reviewer is different again. File review work may happen before appraisal, during claim development, or when a stakeholder needs a clearer summary of disputed issues. Confirming the role first keeps expectations clean and helps protect the process.