Well, yes matter implies energy.
Dark Matter and Dark Energy should not be confused, they are two different things completely. They just have been given the term dark cause we can't directly observe them.
"Dark matter" is inferred to exist based on observed gravitational effects on visible matter and background radiation. The evidence for this is a lot more solid than that of Dark Energy - though some people have suggested we just have gravity wrong or we just dont have sensitive enough telescope to find the normal matter. Essentially dark matter means it does not radiate electromagnetically. Dark matter was postulated by Fritz Zwicky in 1934, to account for evidence of "missing mass". He is quite an interesting character, but that's a discussion for another time. The majority of the dark matter in is believed to be nonbaryonic, that is it contains no atoms and does not interact with ordinary matter via electromagnetic forces (an example would be a neutrino). This is where CERN is important for astrophysics.
"Dark Energy" - is essentially a fudge factor. The mistake that Einstein made and actually went on to make some sense, maybe. The most common form is the cosmological constant, a constant energy density filling space homogeneously.
