APIs for querying your data (PageQuery, StaticQuery, Fragments) and specifying your GraphQL schema (schema customization).
Covers PageQuery, StaticQuery and the useStaticQuery hook.
Covers sort, filter, skip, limit, formatting dates and excerpts, query variables, grouping, fragments, aliasing, and conditionals.
In situations when you either want to explicitly define the data shape, or add custom functionality to the query layer, you can override Gatsby's auto-inferred schema.
Fragments allow you to reuse parts of GraphQL queries. It also allows you to split up complex queries into smaller, easier to understand components.