What's on the dark side of the moon and how do you know

hmm lets see
1. speak to me/breathe
2. on the run
3. time
4. the great gig in the sky
5. money
6. us and them
7. any colour you like
8. brain damage
9. eclipse

its on the back of the cd.

There is NO dark side of the moon.

There is a FAR side that never faces Earth, but that side gets just as much sunlight as the side facing earth.

What is on the Far side. Not much. It has been completely mapped by camera ships and several men have been in Orbit around the moon and have actually seen it.

Because there is no lunar darkside. All sides get equally illuminated over the course of it rotation.
And for lunar maps -
http://www.nasa.gov/mission_pages/LRO/ne…
http://www.lpi.usra.edu/resources/mapcat…

Aside from Pink Floyd(see Bassita answer), the 'dark side' is same as the 'bright side', except it doesn't have a face on it. We know because we've been there.