This is a HL7 FHIR server, and as you appear to be accessing this page from a web browser you are seeing a HTML version of the requested resource(s). You can also access this URL from a FHIR client as a ReSTful API call. For more details please see the HL7 FHIR specification.
{
  "resourceType": "CodeSystem",
  "id": "CareConnect-InterpretationCode-1",
  "text": {
    "status": "generated"
  },
  "url": "https://fhir.hl7.org.uk/STU3/CodeSystem/CareConnect-InterpretationCode-1",
  "version": "1.0.0",
  "name": "CareConnect Interpretation Code",
  "status": "draft",
  "date": "2019-03-12T00:00:00+00:00",
  "publisher": "HL7",
  "contact": [
    {
      "name": "Interoperability Team",
      "telecom": [
        {
          "system": "email",
          "value": "interoperabilityteam@nhs.net",
          "use": "work"
        }
      ]
    }
  ],
  "description": "This value set defines the set of codes that can be used to indicate the meaning/use of a reference range.",
  "copyright": "Copyright © 2018 NHS Digital",
  "caseSensitive": true,
  "content": "complete",
  "concept": [
    {
      "code": "OR",
      "display": "Outside Reference Range"
    },
    {
      "code": "PA",
      "display": "Potentially Abnormal"
    }
  ]
}