what does parsing data in nodejs mean code example

Example 1: javascript parse json

var jsonPerson = '{"first_name":"billy", "age":23}';
var personObject = JSON.parse(jsonPerson); //parse json string into JS object

Example 2: if json then parse

function isJson(str) {
    try {
        let value = JSON.parse(str);
      	return value
    } catch (e) {
        return str;
    }
}