what is exotic matter?

Question

is it theoretical or is it real and is it true that it has negative weight!!??

Answer 1

If the matter can be weighted its called a mass.
It it cannot be weighted ,then it can be called an exotic mass. Dark matter would fall on that category .
So anything that does not have weight is called masseless.
Light is the lighest mass of the Universe and has weight therefore its not an exotic mass.

Answer 2

well dark matter is thought to be real because the universe is expanding at and accelerating rate. but we cannot prove that its real because we cant see it. anti-matter on the other hand, does exist, which is a sub-atomic particle with the same mass and opposite charge of its normal couterpart. and if a proton and an anti-proton collide it creates a pretty sweet explosion.