How to get Cookie in Postman?

When I call a server "1" in Postman, I got "Cookie" in header. And in real app, if I call another API without this "Cookie", it doesn't work. If I call another API of server "2", there is no "Cookie" in the header. Only when I call a server "1", the "Cookie" appear. What is this "Cookie" in header and how to get this in real app? *when I turn off postman and turn on again, the Cookie value changes.

This is the code that I got when I call server "1".

var myHeaders = new Headers();
myHeaders.append("Content-Type", "application/x-www-form-urlencoded");
myHeaders.append("Cookie", "JSESSIONID=9b8e57bd-33c5-447d-9e77-e64a17412478");

var urlencoded = new URLSearchParams();
urlencoded.append("password", "123123");
urlencoded.append("username", "15515579329");

var requestOptions = {
  method: 'POST',
  headers: myHeaders,
  body: urlencoded,
  redirect: 'follow'
};

fetch("https://jszt.yunlianshe.cn/miniprogram/login", requestOptions)
  .then(response => response.text())
  .then(result => console.log(result))
  .catch(error => console.log('error', error));

This is the body