Dave, dark energy (73% of th invisible Universe) and dark matter (23% of the invisible Universe) are two different things...

Dark energy has to do with the fact (force) that the Universe seems to be expanding and actually accelerating in its expansion, in terms of the relative distances between galaxies, for example...

Dark matter has to do primarily with stuff (matter!) within each galaxy, like in a black hole, etc. In other words, without it, the visible stuff (matter!) within any particular galaxy would all fly away due to the very high spining speeds of any typical galaxy...

This means that there is only about 4% of the Universe which is visible!

-wirelessguru1
The Invisible Universe