what does fetch do? code example

Example 1: javascript fetch api

fetch('http://example.com/movies.json')
  .then((response) => {
    return response.json();
  })
  .then((data) => {
    console.log(data);
  });

Example 2: fetch api

// Error handling while fetching API

const url = "http://dummy.restapiexample.com/api/v1/employee/40";
fetch(url) //404 error
     .then( res => {
          if (res.ok) {
                return res.json( );
          } else {
                return Promise.reject(res.status); 
           }
      })
      .then(res => console.log(res))
      .catch(err => console.log('Error with message: ${err}') );