Definition:
Not all effects happen in a computer. Special effects, abbreviated as SFX, are the physical, practical, on-set techniques used to create illusions and visual elements during filming: explosions, rain, prosthetics, miniatures, breakaway props, and wirework. They exist in the physical world and are captured by the camera on the day.
What It Means in Movies:
Special effects are what happen before post-production begins. A practical explosion is detonated on set. A rain machine produces actual water. A prosthetic wound is applied to an actor's face. The distinguishing quality is physical reality: practical effects create something that the camera, the actors, and the crew are all in the same room with.
Why It Matters:
Practical effects create an on-set reality that performers and cameras respond to authentically. The difference between an actor reacting to a real explosion and an actor reacting to a green screen is visible on their face. Many filmmakers deliberately combine practical effects with VFX, using the practical element as something real for the digital work to composite against.
Example:
The sandstorm sequence in Lagaan was created using practical special effects: wind machines, dirt, controlled-environment work, and strategic location shooting rather than digital augmentation. The result has a physical presence that a purely digital version would struggle to match.