What are the differences between Beckmann and GGX in Glossy shader (Cycles)?

What are the differences between Beckmann and GGX in Glossy shader (Cycles)?

I’m interested as well in what the differences are. All I know about it is that it’s two different algorithms to handle light and reflections.

This may be an interesting read (download abstract as PDF at the bottom of the page).

Thanks, I hope I can understand it!