A dark side of something is a side of that something where, by definition, it is dark. Dark sides can be created by putting a lamp near the desired light side and turning off all the other light. Usually, dark sides are accompanied by shadows, but in the case of the Earth, no shadow has been found yet.
A dark side is characterized by its power, which establishes itself in its full glory when the local power plant stops providing power for the corresponding light side. Ironically, even though constantly asked by various cliché'd evil overlords to do so, Luke Skywalker could never see the true power of the dark side. Actually, he could never see the dark side itself. Maybe you will be more successful, especially with night vision devices.
Dark sides can also be found on the oppositie of black holes. Do not confuse this with wormholes. Wormholes are created by inter-dimensional spaceworms. Wormholes are mysterious tunnels, particularly common in areas of high Swiss cheese density.
A Black hole is an impossible object which makes the Universe work. It has the useful property of being "undetectable". It's like when your spouse comes home with a dent in the car, and blames it on an invisible black mass; the dent is proof of the black mass, but you can't, and never will be able to see it with CCTV cameras, but you know it's there. Also, when you've lost something (like the car keys) and don't want to admit it to your spouse, you can claim the car keys have vanished down a black hole.
Dark matter is an equally undetectable force that causes cars to defy gravity, and hit invisible black holes. Astronomers will tell you that lots of them have spouses with dents in their cars, and can explain this is very technical terms, so you won't be able to understand why it's not possible.
Dark matter is what normal matter becomes after it has been lost, misplaced or otherwise becomes irretrievable. This includes cats, socks, rubber bands and ****.
Dark matter has many uses:
1)Fertiliser
The concentration of dark matter in your neighbour's garden is higher than in yours, due to garden tools he has borrowed from you. Apparently the increased amount of dark matter promotes growth and greenness in your neighbours' garden. Stealing is a great countermeasure.
2) Weapon
If concentrated for more than 20 seconds, it will become a duck. If more than 30 seconds, a black hole. More than 50 seconds, Swiss cheese.
Swiss cheese is a holy, rare breed of cheese. Swiss cheese exists only in the most outer areas of the Universe due to its inherent instability around other cheeses. Some can be found in China, though.
China's pledge: MADE IN CHINA
China is very original. They painted Mona Lisa AND made their own McDonalds Slogan!
Mona Lisa:

McDonalds Slogan:

China good, dark side bad...
