Anti-matter is a particular type of matter which is composed of particles which are antiparticles to particles of matter.
Example:- Positron is an electron which has positive charges, an anti proton is a particle which has negative charge.
Significance of anti-matter is that when matter and anti-matter particles collide a lot of energy is released, in accordance to Einstein's equation, E=mc2
where E is Energy, m is rest mass, c is the speed of light.
In matter antimatter reaction, the entire rest mass is converted into energy, hence the reactions are highly efficient. These reactions are more efficient than nuclear fusion reactions, and much more efficient than reactions used in space fuel. The energy is released at the speed of light from the point of annihilation.
If we could master the technology of conducting matter antimatter reactions, all our energy problems would be solved. About 11-12 picograms of antimatter is produced annually most of which is produced in C.E.R.N( European Organization for Nuclear Research). Antimatter particles are the most expensive components priced at an astounding $300 billion per gram.