Antimatter particles are almost identical to their normal matter counterparts, except they carry the opposite charge and momentum. Though it’s an extremely rare substance, physicists routinely generate antiparticles in particle accelerators. Antimatter is also created naturally in high-energy processes, such as near the event horizons of black holes. How and why the Universe ended up consisting almost entirely of normal matter is an unsolved mystery.
It’s extremely difficult and expensive to create antimatter. The European Laboratory for Particle Physics (CERN) produces antimatter in its Antiproton Decelerator instrument, in which a beam of protons slams into a metal target to create antiprotons. But even this produces no more than a few tens of thousands of particles.