From SA Mafia Wiki
The Night phase follows the Day phase of Mafia games. During the Night, all roles with active abilities get to carry out their night actions, such as investigations, protections, roleblocks, and nightkills, to name a few. The Night phase is also characterized by silence; no extra discussion takes place unless it is done privately.
Some games feature a Night 0 that occurs before the first Day. Many games also feature a Twilight phase that occurs after the execution but before the Night. During the Twilight, players can (for a short time) discuss cardflips and other important things before the Night begins.