What are GraphQL object types and how do you define them?

An object type describes one kind of entity in your domain, like a user or a post. It lists the named fields a client can ask for. Object types are the most common type in a GraphQL schema.

You define one in the Schema Definition Language (SDL) with the type keyword, a name and typed fields. A field can return a scalar like String! or another object type like User!. That is how types link: User.posts returns posts, and Post.author returns a user.

The root Query type is an object type too. Its fields are the entry points for reading data.

type User {
  id: ID!
  name: String!
  email: String!
  posts: [Post!]!
  createdAt: String!
}

type Post {
  id: ID!
  title: String!
  content: String!
  author: User!
  published: Boolean!
}