According to wikipedia, tilt-shift photography refers to the use of tilt and a large aperture to achieve a very shallow depth of field.
It sounds complicated. Simply what I like about this technique is it can make your photo look like a miniature model.
I found a website which can transform your normal photo to a "tilt-shifted" photo:
http://tiltshiftmaker.com/ .I tried it my own and the result is quite pleasing.
This is my original photo taken during my "Norway in a nutshell" tour - a village on Sognefjord:
And this is the photo after being applied tilt-shift technique:
It's nice isn't it? ;)