The Nosgoth Free Weekend is a four day event before the beta starts, when you can play the game for free via Steam. All you need is a Steam account and if you play it you will receive double XP and an in-game emblem.
The event will start on August 7, and until August 10 you will be free to play the game. More details can be found here FAQ. This is a good opportunity to try out the game in order to see if you like it or not.
Nosgoth is expected to be release in winter with no specific date.