I still don't understand what mafia is.
Can someone briefly explain me the concept?
It is a forum game.
There will be a host(s) depending on the game. After you have signed up for a game, the hosts will send out roles to everyone who signed up in PM.
These roles can be town (good guys), Mafia or other scum group (bad guys), and Neutrals which can be many different things from just wanting to survive until the end of the game, or kill every last player in the game.
The two main cycles of the game is Day Phase & Night Phase. During the Day phase is when all the players join in on the thread and talk, town tries to find the scum players in the game, while scum tries to act as if they are town. Votes are also placed on players during this phase to pick a lynch candiate they believe is scum, if a person is lynched, they are removed from the game.
Night time, is when there is no talking in the game thread (special situations might apply the host will inform you of). Everyone send in their actions from the roles they were given from the host, which can be any number of abilities from Invests to Kills.
The host will then workout all the night actions and start the dayphase posting the results of the night listing any kills that may have occured.
It continues in these cycles until the game is won.
I will answer any other specific questions you have, just let me know.