Base URL
The base URL of the service is typically https://localhost:3000 .
The API reference documents this as {base_url}/users or {base_url}/sightings for example. This is because you can configure the port number for json-server to something other than 3000.
If Orca Sightings were an actual cloud service, the URL would be something like https://api.orca-sightings.com/v1 .