I just recently discovered this. Basically, by changing the tilt of the camera, you can make objects appear smaller than they actually are. Wikipedia’s take on it:
“Tilt-shift photography” refers to the use of camera movements on small- and medium-format cameras, and sometimes specifically refers to the use of tilt for selective focus, often for simulating a miniature scene. Sometimes the term is used when the shallow depth of field is simulated with digital post processing; the name may derive from the tilt-shift lens normally required when the effect is produced optically.
image from smashingmagazine.com
image from spoonfeddesign.com
image from amazingmoments.info
These are just a few of the many fantastic examples of tilt shift photography.
Cool, huh?