Some candidates for dark matter are so-called massive compact halo objects (MACHOSs), a category which includes black holes, asteroids and giant Jupiter-like planets. We would not see such objects in a galaxy, because they do not shine, but they would all contribute to the gravitational attraction within a galaxy. Other candidates for dark matter come under the heading of weakly interacting massive particles (WIMPs), which includes various types of particles that do not form objects like MACHOS but which might permeate the entire universe, hardly making their presence felt, except through the force of gravity. - Big Bang, Simon Singh

The book then goes onto talk about dark energy but since scientists haven't the foggiest idea about dark energy yet, they haven't quite found really cool names for it yet.

Simon Singh writes great books, that make science accessible for the uninitiated and a joy for those who thinks that scaffolding can be as interesting as the ancient building it's erected around to clean. (Hint buy the book, I give it 5 quasars out of 5 or a "it's damn fucking good")