What is GraphQL?
A query language for APIs that lets clients request exactly the data they need in a single request.
GraphQL was open-sourced by Facebook in 2015 to solve the over-fetching problem of REST APIs: with REST, you call `/users/123` and get back the full user object even if you only need the name. With GraphQL, you write a query that names the exact fields you want, and the server returns just those. Strong typing via a schema. Single endpoint (`/graphql`) regardless of resources. The tradeoff: more setup, more concepts to learn. REST remains the default for most marketing sites; GraphQL is common in larger apps with many client types (web + mobile + internal tools).