PAID ONLINE COURSES FOR FREE SEPTEMBER 4, 2018

How does this works? I tried to download a course and I see a link with 'Activate Udemy Free Coupon Code ' . Then it takes me to an udemy page and asks me to pay for it.
Sorry, if you can explain it would be nice, ty!

Thanks bro it looks very helpfil I will try it and back to you

thanks. but please explain and not just put a link that would be wonderful.