HL7 FHIR R4

1. RESTful API

   FHIR REST interactions: read, vread, create, update, patch, delete, history, conditional operations, batch and transaction, and ETag/versioning headers.

2. Search

   Search parameter types, modifiers, prefixes, _include and _revinclude, chaining, _count paging, and sorting.

3. Data types

   Primitive and complex types such as Identifier, CodeableConcept, Coding, Reference, Period, Quantity, and Money.

4. Bundle

   Bundle types (searchset, transaction, batch, document, message), entry.fullUrl, and transaction reference resolution.

5. Patient

   Patient demographics, identifiers, name and address, contact, managingOrganization, and link for merged records.

6. Encounter

   Encounter class, status, type, period, participants, diagnosis, hospitalization, and serviceProvider.

7. Claim and ClaimResponse

   Claim use, type, insurance, diagnosis, procedure, item and adjudication elements, and how ClaimResponse returns the payer outcome.

8. ExplanationOfBenefit

   EOB structure for adjudicated claims: item.adjudication, total, payment, benefitBalance, and how it differs from Claim.

9. Coverage

   Coverage subscriber, beneficiary, payor, class and plan, period, relationship, order, and cost-to-beneficiary.

10. Observation

    Observation status, category, code, value[x], components, referenceRange, and vital signs and lab usage.

11. Profiling and extensions

    StructureDefinition profiles, constraints, slicing, must-support, and extensions via extensibility.

12. Terminology

    CodeSystem, ValueSet, ConceptMap, binding strengths, and the $expand, $validate-code and $lookup operations.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.