What Is GraphQl

GraphQl - is query language.
A way you can quickly and clear explain what kind of data you want
Graphql can be compared to REST API:

In REST:

By sending request to "/users" url you telling server that you asking for users
By sending request to "/users/123" url you telling server that you asking for user with id 123

In GraphQl

the ways to "explain" to server what exactly you want are much wider:
Here is example how we can achieve the total repos count of user, only instead of using v3 GitHub api (like in previous posts)
we using GitHub grpahQL v4 api:

function getReposCount(user) {
  // graphQL query
  const query = `query {
     user(login: ${user}) {
       repositories {
         totalCount
       }
     }
  }`;

  const body = JSON.stringify({ query });

  const uri = `https://api.github.com/graphql`;
  return fetch(uri, {
    method: "POST",
    headers: { Authorization: `bearer ${token}` },
    body
  })
  .then(d => d.json())
  .then(data => {
    // extract only count field
    const {
      data: {
        user: {
          repositories: { totalCount: total }
        }
      }
    } = data;
    return total;
  });
}