How Queries Work
In Gatsby, GraphQL queries are specified as tagged graphql expressions. These can be exported in your page source files, used in the StaticQuery component, or used in the useStaticQuery hook in your React code. Plugins can also define fragments for use in queries.
Note that the process outlined in this section only applies to queries that are specified in components or templates. It does not apply to queries specified in a gatsby-node.js file which are typically used for the creation of dynamic pages. (For an example of a query in a gatsby-node.js file, check out the Creating Pages section from Part 7 of the Gatsby tutorial.
Most code to do with queries is in the src/query directory in the Gatsby monorepo.
There are two steps involved in the lifetime of a GraphQL query in Gatsby. The first is extracting and validating it, and the second is running it.