Three.js-101-:-Hello-World!.md

@@ -30,7 +30,25 @@ The first thing you need to use three.js is a simple HTML page. you can start wi
 </html>
 ```
 ## Initialize three.js
+
+In order to use the three.js library, first you need to add it as a script to your HTML page. you can add the flowing code to the head section.
 ```
 <!-- three.js -->
   <script src="https://unpkg.com/three@0.126.0/build/three.js"></script>
-```
+```
\ No newline at end of file
+
+## WebGlRenderer, Scene and Camera
+This is the first common pattern we are going to see in every Three.js app.
+
+- Create a Renderer.
+- Create a Scene.
+- Create a Camera.
+The renderer is the place where we are going to put the result of our scene. In Three.js we can have multiple scenes and each one can have different objects.
+
+![image](uploads/d21895e6a5457bebfc3ded3e5b5b652c/image.png)
+
+Here we create our WebGLRenderer, we pass it the size of the window as a parameter and then append it to the DOM.
+
+
+
+