An external viewer sees one asset's current or latest reported location and movement history, and nothing else. They cannot see telemetry, documents, maintenance information, other equipment, sites, people or platform modules, and they never receive a login to your organization.
This is the difference between letting a customer follow one machine and giving them access to your fleet. If someone needs platform data beyond that location-only view, they need a SolidTrack user account with the appropriate internal scope.