<s>[INST] What are dark matter and dark energy and how do they affect the structure and evolution of the cosmos? [/INST] Dark matter is a form of matter that does not emit, absorb, or reflect light, which makes it invisible to telescopes.  Despite this, its existence is inferred from its gravitational effects matter that is visible.

Dark energy is an enigmatic form of energy that permeates all of space and is responsible for the observed acceleration of the expansion of the universe.

Together, dark matter and dark energy profoundly impact the structure and evolution of the universe.  Dark matter provides the gravitational force needed for galaxy formation and helps maintain their structure.  Dark energy counteracts the attractive force of gravity, causing the universe to expand at an accelerating rate. 

The interplay between dark matter and dark energy determines the fate of the universe.  If dark energy continues to dominate, the universe will keep expanding faster and faster, eventually leading to a scenario known as the "Big Rip." </s><s>[INST] so are Dark energy and dark matter two completely different things? [/INST] Dark energy and dark matter are separate things that arise to solve different problems.

Dark energy is the rational for tuning the cosmological constant term in Einstein's field equations to explain the observed expansion of the universe.  (Antidotally, the cosmological constant is a term Einstein added to make the universe not expand or contact in his model.  He later regretted the addition, terming it "his greatest blunder", but it later became a tool to address this issue.)

Dark matter is the rational to explain a wide array of observations where gravitational calculations suggest there is much more mass than we currently estimate from visual observations.  This manifests as a line in the balance sheet for the mass in the universe as cosmologist's make an accounting of it.

As the names suggest, we don't know much about dark energy or dark matter, and many theories abound to try to explain these discrepancies.  There may be a relationship between the two, but such a link is not implied a priori. </s>