Dark matter is matter of an unknown type. It is known to exist, due to its gravitational influence, but it is not known what it is made of. There is at least 5 times as much dark matter than "normal" matter.
No, this is not possible. Dark matter is a form of matter that is undetectable by human senses, because it does not interact with any of the four fundamental forces that affect the visible universe (electromagnetism, strong nuclear force, weak nuclear force, and gravity). Therefore, it is impossible for dark matter to become normal matter as observed at a human sensory level.
Mainly that dark matter interacts with dark matter and with normal matter via the gravitational force; and that it DOES NOT interact with normal matter via any other known force. Or, if there is any interaction, it does so to such a small extent that it hasn't been possible to detect this so far.