Why does Profile class use the .call and .emit methods and why is it is assigned 'this'.

var EventEmitter = require("events").EventEmitter;
function Profile(username) {
    // ❓👇🏽 What is the purpose of this .call method?
    EventEmitter.call(this);
    // ❓👇🏽 A reference to the object is created to emit 'end', 'data', and 'error'. 
    // Why not just use 'this' instead to refer to the Profile object?
    profileEmitter = this;

    //Connect to the API URL (https://teamtreehouse.com/username.json)
    var request = https.get("https://teamtreehouse.com/" + username + ".json", function(response) {
        var body = "";

        if (response.statusCode !== 200) {
            request.abort();
            //Status Code Error
            profileEmitter.emit("error", new Error("There was an error getting the profile for " + username + ". (" + http.STATUS_CODES[response.statusCode] + ")"));
        }

        //Read the data 
        response.on('data', function (chunk) {
            body += chunk;
            profileEmitter.emit("data", chunk);
        });

        response.on('end', function () {
            if(response.statusCode === 200) {
                try {
                    //Parse the data
                    var profile = JSON.parse(body);
                    profileEmitter.emit("end", profile);
                } catch (error) {
                    profileEmitter.emit("error", error);
                }
            }
        }).on("error", function(error){
            profileEmitter.emit("error", error);
        });
    });
}

studentProfile.on("end", console.dir); // here I've included how its printed to console.