Let's start with the big thing! In this lesson I'll show you the functions. You'll see that it is divided into a couple of sections with an exercise in the middle.
You will see this structure often throughout the course: an introduction, with an exercise to practice. Don't go on to the next lesson until you have tried it, since you will find the solution there.
It is very important that you try to do the exercises before seeing how they are resolved. What is not practiced, is forgotten.