It's not just a language or a subject in school, but a billiard technique. You've probably toyed with the technique on your own if you've been practicing everything you've learned so far. It is, after all, the next logical step.

English is sidespin. Now that you know how and where to hit the ball, it's time to learn how to really control your shots with spin. English makes the cue ball spin across the table when you hit it to the left or right of the vertical axis (left or right of center). What you're doing is using a forward and a sideward thrust at the same time.

You shouldn't use English just to show that you know how to use it. There are specific times and reasons you will need it and it should only be used if there are no other options available.