You can find this small tutorial text in the game as well, by pressing F1.
It's all about versus
A small group of Traitors is randomly picked.
Together they have to kill all the Innocent.
The Innocent do not know who is a Traitor and who isn't.
The Traitors must use this fact, because they are outnumbered.
If you die, you will not respawn until next round.
Innocents will not know you are dead until they find your corpse.
Corpses may have information that leads to the killer.
Traitors can buy special equipment.
Their Equipment Menu can be opened by pressing C.
Innocent players who were selected as Detectives may also buy
special detective equipment, which can help them find the Traitors.
As Innocent, do not kill too easily! Killing other Innocents costs you a lot of points and Karma.
As Traitor, hide the body! Innocents get valuable info from corpses.
As Traitor, communicate and cooperate! Cause distractions,
As Detective, search bodies! All Innocents can
see and use the results you find.
Q will drop your weapon so you can pick up another.
C will open the Equipment Menu, if you are Traitor or Detective.
Shift sends voicechat only to other Traitors.
F1 shows the Help and Settings menu.
Set a key for Suit Zoom in your settings to use Radio Commands.
Your Karma starts at 1000 and goes down if you damage players who are on your own side.
If your Karma is low when a round starts, you get a penalty to your damage that round.
By playing clean rounds where you don't harm teammates, you regain Karma.
The Karma value shown on the scoreboard updates only after the round ends.
Check the full Help for more details.