Current definitions:

Purpose: Explanation of why this value set is needed and why it has been designed as it has.

Description: A free text natural language description of the value set from a consumer's perspective. The textual description specifies the span of meanings for concepts to be included within the Value Set Expansion, and also may specify the intended use and limitations of the Value Set.

useContext: The content was developed with a focus and intent of supporting the contexts that are listed. These contexts may be general categories (gender, age, ...) or may be references to specific programs (insurance plans, studies, ...) and may be used to assist with indexing and searching for appropriate value set instances.

In light of @JIRA-25272 request for new element for valueSet.scope, the definitions of these elements should be reviewed and clarified. Currently (R4) an alternate name for Description is Purpose. (see JIRA-24085).