title: let { var} definition - what is it
body: <p>I'm want to learn GraphQL and in the documentation there is a start up code to run on node.js with express framework:</p>
  
  <pre><code>var express = require('express');
  var graphqlHTTP = require('express-graphql');
  var { buildSchema } = require('graphql');
  
  var schema = buildSchema(`
    type Query {
      hello: String
    }
  `);
  
  var root = { hello: () =&gt; 'Hello world!' };
  
  var app = express();
  app.use('/graphql', graphqlHTTP({
    schema: schema,
    rootValue: root,
    graphiql: true,
  }));
  app.listen(4000, () =&gt; console.log('Now browse to localhost:4000/graphql'));
  </code></pre>
  
  <p>Every thing is running properly but I dont understand this line:</p>
  
  <pre><code>var { buildSchema } = require('graphql');
  </code></pre>
  
  <p>Why there are curly braces? For what?</p>