This is where I store copies of CodeWars challenges (aka katas) I completed.
It's a programmer's community targeted on training yourself upon challenges in many different programming languages. Challenges are categorized into different skill levels called Kyū. As you progress your rank increases. It's a great way of upping your coding game community-style. You get to see other coder's solutions once you've completed a kata yourself. This massively improves your skills as after you've had to wrap your brain around a problem and its solution you get to see how others did it (and prosumably better than you). I've never learnt faster and it's great to see other people's way of problem solving.