The Universe’s divisions of the “mass-energy density” (given in percentages) are based on the Lambda-CDM (ΛCDM) model of the Big Bang theory, in which CDM stands for Cold Dark Matter, and Lambda (Λ) is the symbol denoting the ”Cosmological Constant” that supposed to represent Dark Energy or Vacuum Energy. Dark Matter & Dark Energy have opposite casualties and effects on cosmic gravitation.
ΛCDM was the latest model (the 4th model) to be developed for the Big Bang theory in the late 1990s, to explain the “formation” & “distribution” of large-scale structures (eg molecular clouds, galaxies, galactic clusters, etc) of the universe, explain the abundance of light elements (hydrogen, helium) in the early universe, explain the missing masses - Dark Matter - that keep each galaxy together, and to explain what drive drive the Universe expansion - Dark Energy.
The theoretical astrophysicists & cosmologists have reused Albert Einstein‘s Cosmological Constant (Λ) that was meant to be used with his failed Static Universe hypothesis (1917); the constant was meant to be used with the Einstein Field Equations (EFE) for General Relativity.
Anyway, ΛCDM divide the mass-energy densities between baryonic matters (all the atomic elements in the Periodic Table, and the molecules), Dark Matter & Dark Energy.
if you recall, Einstein was one who developed the Special Relativity’s most iconic equation (1905) - E = mc^2 - was the equation that explained relationship between mass and energy, hence his Mass-Energy Equivalence.
NASA WMAP & ESA Planck were the space missions that measured & calculated these distribution of mass-energy densities. The actual percent for Dark Energy is actually 69% for Planck (2013) and 72.8% for WMAP (2012), not your 95%.
Dark Matter makes up 26.8% (WMAP 22.7%). And baryons 4.82% (WMAP 4.56%).
The 95% come from the sum of Dark Matter & Dark Energy.
Dark Energy is why causing the Universe to expand, and accelerating its expansion. while Dark Matter is what holding galaxies together, including the spiral outer arms rotating at the same speed as the inner arms. Our Milky Way wouldn’t exist if it were for Dark Matter.