Special effects (often abbreviated as SFX, SPFX, or simply FX) are illusions or visual tricks used in the film, television, theatre, video game, and simulator industries to simulate the imagined events in a story or virtual world. Special effects are traditionally divided into the categories of optical effects and mechanical effects. With the emergence of digital filmmaking a distinction between special effects and visual effects has grown, with the latter referring to digital post-production while "special effects" referring to mechanical and optical effects.