From Disney's Hollywood Studios Wiki
In film, the term 3-D (or 3D) is used to describe any visual presentation system that attempts to maintain or recreate moving images of the third dimension, the illusion of depth as seen by the viewer.
The technique usually involves filming two images simultaneously, with two cameras positioned side by side, generally facing each other and filming at a 90 degree angle via mirrors, in perfect synchronization and with identical technical characteristics. When viewed in such a way that each eye sees its photographed counterpart, the viewer's visual cortex will interpret the pair of images as a single three-dimensional image. Modern computer technology also allows for the production of 3D films without dual cameras.
4-D is a similar term for a 3-D Movie with some live elements, such as water spraying, or smells.
 Studios Reference
Toy Story Midway Mania! is a ride with many 3-D Game Stops, and each has a few 4-D effects, including water spraying and air compressors.