What are fragments in GraphQL?

Fragments are reusable units of fields that can be shared across multiple queries. They help avoid repeating the same set of fields. Define a fragment with fragment UserFields on User { id name email avatar } and use it with the spread operator: { user(id: "1") { ...UserFields } }. Fragments must specify the type they apply to (on User) to ensure type safety. They are especially useful in front-end codebases (with tools like Apollo Client) where multiple components need the same fields from a shared type, promoting colocation of data requirements with UI components.