Dark matter: Neutrinos are not dark matter, although they may be part of the story, but they have properties quite similar. They can pass through the earth easily without interacting. Also they don't clump together. Atoms are mostly empty space. Ordianry matter is held together by electrical force. Neutrinos and dark matter appear to ignore it.

Dark energy: The use of Einstein's cosmological constant (he was the one who tried to get rid of it) is a tentative idea to explain dark energy. If theoreticians develop a better idea, the cosmo constant would be discarded. However, dark energy is there!