Field service covers any job where staff travel to the customer: an engineer fixing a boiler, a fitter installing shelving, a surveyor inspecting a site. The difficulty is coordination, because the people doing the work are away from the office when plans change.
Field service software helps by giving the office a live picture and the engineer a simple mobile view. Jobs are scheduled, the engineer sees the address and notes, completes a checklist, captures photos and a signature, and the invoice can follow without paperwork being retyped back at base.