The query you've provided is an introspection query that retrieves metadata about a GraphQL schema's structure14.

Breaking down what this query does:

• __schema - Accesses the introspection field that exposes the entire schema's capabilities5
• queryType { name } - Returns the name of the root Query type available on the server1
• types { name } - Fetches a list of all types supported by the GraphQL server5
• directives { name } - Retrieves the names of all directives defined in the schema2

This is a simplified version of what's often called "the introspection query"3. When executed against a GraphQL API, it returns a JSON response containing the names of the query type, all available types in the schema, and all directives—providing a high-level overview of what the API can do12.

Introspection queries like this are used to enable live schema documentation and power GraphQL development tools, such as GraphQL Playground, allowing developers to explore and understand an API's capabilities at runtime24.