diff --git a/app/controllers/auth.controller.js b/app/controllers/auth.controller.js
index d455114..d97e08b 100644
--- a/app/controllers/auth.controller.js
+++ b/app/controllers/auth.controller.js
@@ -1,3 +1,5 @@
+// Registration and Login controller
+
 const config = require("../config/auth.config");
 const db = require("../models");
 const User = db.user;
@@ -6,31 +8,37 @@ const Role = db.role;
 var jwt = require("jsonwebtoken");
 var bcrypt = require("bcryptjs");
 
+// Registration logic
 exports.signup = (req, res) => {
+  // create a user instance
   const user = new User({
     username: req.body.username,
     email: req.body.email,
     password: bcrypt.hashSync(req.body.password, 8)
   });
-
+  
   user.save((err, user) => {
+    // if there is an error while creating a user instance
     if (err) {
       res.status(500).send({ message: err });
       return;
     }
 
+    // if the user request contains a specified role  
     if (req.body.roles) {
       Role.find(
         {
           name: { $in: req.body.roles }
         },
         (err, roles) => {
+          // if the role is not found
           if (err) {
             res.status(500).send({ message: err });
             return;
           }
-
+          // else save the role and map it to the respective role id
           user.roles = roles.map(role => role._id);
+          // save the user
           user.save(err => {
             if (err) {
               res.status(500).send({ message: err });
@@ -42,6 +50,7 @@ exports.signup = (req, res) => {
         }
       );
     } else {
+      // this role is the default role of the application
       Role.findOne({ name: "user" }, (err, role) => {
         if (err) {
           res.status(500).send({ message: err });
@@ -62,7 +71,9 @@ exports.signup = (req, res) => {
   });
 };
 
+// Login logic
 exports.signin = (req, res) => {
+  // check if username exists in the server
   User.findOne({
     username: req.body.username
   })
@@ -72,11 +83,13 @@ exports.signin = (req, res) => {
         res.status(500).send({ message: err });
         return;
       }
-
+      
+      // if user does not exist in the server
       if (!user) {
         return res.status(404).send({ message: "User Not found." });
       }
-
+      
+      // compare the provided password to the password in the server
       var passwordIsValid = bcrypt.compareSync(
         req.body.password,
         user.password
@@ -88,16 +101,20 @@ exports.signin = (req, res) => {
           message: "Invalid Password!"
         });
       }
-
+      
+      // create token
       var token = jwt.sign({ id: user.id }, config.secret, {
         expiresIn: 86400 // 24 hours
       });
-
+      
+      // create authorities array: a new name for all the roles in the roles array after adding the prefix..
       var authorities = [];
-
+      
+      // for each role in the roles array, add the prefix ROLE_, and convert the role name to uppercase
       for (let i = 0; i < user.roles.length; i++) {
         authorities.push("ROLE_" + user.roles[i].name.toUpperCase());
       }
+      // return the user details
       res.status(200).send({
         id: user._id,
         username: user.username,
diff --git a/app/controllers/user.controller.js b/app/controllers/user.controller.js
index e2fa15b..6cba29b 100644
--- a/app/controllers/user.controller.js
+++ b/app/controllers/user.controller.js
@@ -1,3 +1,13 @@
+// Controller for testing Authorization..
+
+// It contains four functions:
+
+//    allAccess for public access
+//    userBoard for loggedin users (any role)
+//    adminBoard for moderator users
+//    moderatorBoard for admin users
+
+
 exports.allAccess = (req, res) => {
   res.status(200).send("Public Content.");
 };
diff --git a/app/middlewares/authJwt.js b/app/middlewares/authJwt.js
index dad88dd..2e73433 100644
--- a/app/middlewares/authJwt.js
+++ b/app/middlewares/authJwt.js
@@ -4,6 +4,7 @@ const db = require("../models");
 const User = db.user;
 const Role = db.role;
 
+// token is obtained from the http header and verified
 verifyToken = (req, res, next) => {
   let token = req.headers["x-access-token"];
 
@@ -20,6 +21,7 @@ verifyToken = (req, res, next) => {
   });
 };
 
+// check if user role is an admin..
 isAdmin = (req, res, next) => {
   User.findById(req.userId).exec((err, user) => {
     if (err) {
@@ -51,6 +53,7 @@ isAdmin = (req, res, next) => {
   });
 };
 
+// check if user role is a manager..
 isModerator = (req, res, next) => {
   User.findById(req.userId).exec((err, user) => {
     if (err) {
diff --git a/app/middlewares/verifySignUp.js b/app/middlewares/verifySignUp.js
index 69801db..3304f2e 100644
--- a/app/middlewares/verifySignUp.js
+++ b/app/middlewares/verifySignUp.js
@@ -3,7 +3,7 @@ const ROLES = db.ROLES;
 const User = db.user;
 
 checkDuplicateUsernameOrEmail = (req, res, next) => {
-  // Username
+   // check if Username exist in the server.
   User.findOne({
     username: req.body.username
   }).exec((err, user) => {
@@ -17,7 +17,7 @@ checkDuplicateUsernameOrEmail = (req, res, next) => {
       return;
     }
 
-    // Email
+    // Check if Email exist in the server.
     User.findOne({
       email: req.body.email
     }).exec((err, user) => {
@@ -35,10 +35,12 @@ checkDuplicateUsernameOrEmail = (req, res, next) => {
     });
   });
 };
-
+// check if the role the user choose exists in the server.
 checkRolesExisted = (req, res, next) => {
   if (req.body.roles) {
+    // loop through the roles array
     for (let i = 0; i < req.body.roles.length; i++) {
+      // if role specified is not in the roles array
       if (!ROLES.includes(req.body.roles[i])) {
         res.status(400).send({
           message: `Failed! Role ${req.body.roles[i]} does not exist!`
diff --git a/app/routes/auth.routes.js b/app/routes/auth.routes.js
index dcfb044..1afdaea 100644
--- a/app/routes/auth.routes.js
+++ b/app/routes/auth.routes.js
@@ -1,3 +1,5 @@
+// Authorization routes
+
 const { verifySignUp } = require("../middlewares");
 const controller = require("../controllers/auth.controller");
 
@@ -9,7 +11,7 @@ module.exports = function(app) {
     );
     next();
   });
-
+  // Signup route
   app.post(
     "/api/auth/signup",
     [
@@ -18,6 +20,6 @@ module.exports = function(app) {
     ],
     controller.signup
   );
-
+  // Login route
   app.post("/api/auth/signin", controller.signin);
 };
diff --git a/app/routes/user.routes.js b/app/routes/user.routes.js
index 0b2b2fa..183c20f 100644
--- a/app/routes/user.routes.js
+++ b/app/routes/user.routes.js
@@ -9,17 +9,20 @@ module.exports = function(app) {
     );
     next();
   });
-
+  // Get contents for public
   app.get("/api/test/all", controller.allAccess);
 
+  // Get contents for all users
   app.get("/api/test/user", [authJwt.verifyToken], controller.userBoard);
 
+  // Get contents for moderators 
   app.get(
     "/api/test/mod",
     [authJwt.verifyToken, authJwt.isModerator],
     controller.moderatorBoard
   );
 
+  // Get contents for admin
   app.get(
     "/api/test/admin",
     [authJwt.verifyToken, authJwt.isAdmin],