SCI stands for "Sierra's Creative Interpreter". Sierra continued with this enhanced engine in 1988, ending the era of the AGI engine.
The SCI was revolutionary in many ways. It was the first game engine ever that supported soundcards and synthesizers such as the legendary Roland MT-64. SCI also introduced mouse support and supported a higher resolution. The engine has 3 main versions, each with multiple sub-versions. The main versions distinguish themselves by the graphics it supported. SCI0 supported EGA graphics, SCI1 supported VGA graphics and SCI95 supported SVGA graphics.