Tilt shift photography is:

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 postprocessing; the name may derive from the tilt-shift lens normally required when the effect is produced optically.

It is a neat way of making an image. Someone applied it to a bunch of Vincent Van Gogh paintings:Tilt-Shift Van Gogh. Fun.