Antimatter, by definition, is particle with the same as as the corresponding particle but with opposite charge and other properties such as magnetic properties. For almost everything, it is possible to have an antiparticle. For example, the antiplarticle of the electron is a positively charged particle known as the positron. It has the same mass as the negatively charged electron, but it has a positive electric charge. Antinuclei, composed of antiprotons and antineutrons and orbited by positrons, can form antiatoms.
Antimatter can be produced in particle accelerators in labs.