This is the NetHack Cross-Variant Summer Tournament. It runs annually during June.
NetHack is a classic roguelike game. If you don't know what that is, try using a Google search.
You can check out tournament rules from the rules page.
There is a list of available trophies and competitions on the trophies page.
This tournament utilizes existing public NetHack servers, such as nethack.alt.org. There are servers in both sides of the Atlantic for low latencies. People not living in Europe or Americas may find it harder to find a low latency server.