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.
<CodeSystem xmlns="http://hl7.org/fhir">
<id value="CareConnect-ConditionCategory-1"></id>
<text>
<status value="generated"></status>
</text>
<url value="https://fhir.hl7.org.uk/STU3/CodeSystem/CareConnect-ConditionCategory-1"></url>
<version value="1.1.0"></version>
<name value="Care Connect Condition Category"></name>
<status value="draft"></status>
<date value="2018-11-14T00:00:00+00:00"></date>
<publisher value="HL7 UK"></publisher>
<description value="A CodeSystem to identify the category of a condition."></description>
<copyright value="Copyright © 2016 HL7 UK"></copyright>
<caseSensitive value="true"></caseSensitive>
<content value="complete"></content>
<concept>
<code value="problem-list-item"></code>
<display value="Problem List Item"></display>
<definition value="An item on a problem list which can be managed over time and can be expressed by a practitioner (e.g. physician, nurse), patient, or related person."></definition>
</concept>
<concept>
<code value="encounter-diagnosis"></code>
<display value="Encounter Diagnosis"></display>
<definition value="A point in time diagnosis (e.g. from a physician or nurse) in context of an encounter."></definition>
</concept>
<concept>
<code value="presenting-complaint"></code>
<display value="Presenting Complaint"></display>
</concept>
<concept>
<code value="co-morbidity"></code>
<display value="Co-morbidity"></display>
</concept>
<concept>
<code value="issue"></code>
<display value="Issue"></display>
</concept>
</CodeSystem>