What is a GraphQL Mutation?

A GraphQL mutation, is a "write, followed by a fetch" - in this case, the GraphQL client sends data to the GraphQL server, expecting some sort of result back.

As an example, this snippet of GraphQL might "like" a post, and return the updated number of likes as a result.

mutation {
  likePost(postID: 1002) {
    post {
      likeCount
    }
  }
}