Caption: A pie chart showing the calculated distribution of the observable universe mass-energy. Features:

1. Note the values have some uncertainties. Other sources will give slightly different sets of values, but all sets will probably agree or nearly to within uncertainty.

2. Dark energy makes up 74 % and dark matter makes up 22%. Baryonic matter (i.e., ordinary matter) makes up only 4% of the mass-energy of the universe. And most of the baryonic matter is nearly invisible baryonic dim matter---mostly intergalactic medium (IGM) (made of hydrogen and helium gas) and some amount of mass-energy in compact remnants and brown dwarfs.

3. The shown distribution is that implied the concordance model (see Wikipedia: Concordance model: Parameters).

4. In special relativity mass and energy are essentially the same thing (seen in two different aspects) because of mass-energy equivalence (formulated as E=mc**2 AKA the Einstein equation)---and so in special-relativity speak, we often use the term mass-energy to emphasize the mass-energy equivalence.

5. The dark energy is a name that covers our ignorance.

   There is no consensus theory of what it is.

   In the concordance model, the dark energy is gives rise to the cosmological constant.

   Really dark energy may be more complex than than a simple cosmological constant.

   It may give rise to an effectively non-constant cosmological constant---in which case we should call the cosmological constant something else: e.g., the cosmological parameter.