What are dark matter and dark energy, and how are they affecting the universe?

Answer 1

Dark matter and dark energy are inventions by astronomers to try to explain a situation the may not exist.
Newtons laws are applied to a solar system like ours,because it is a satellite system.
Galaxies are assumed to be satellite systems also.
If they were dark energy would be required to keep them from flying apart.
There is good reasons to believe that galaxies are something else.

Answer 2

Dark matter and dark energy are hypothetical constructs, the sole set of properties of which is that set required to explain the set of observed yet not yet explainable properties of the universe.

In other words, these have no effect on the universe, but are merely placeholders in some scientists attempts to understand it.