What is matter and anitmatter?

Answer 1

Antimatter has particles with properties that are the opposite of normal matter (in some of their properties). For example, normal matter - the one we are most familiar with - consists of atoms that have protons with a positive charge, electrons with a negative charge, and neutrons, which are electrically neutral. In antimatter, there are anti-protons with a negative charge, anti-electrons (also know as "positrons") with a positive charge, and anti-neutrons (which are also neutral, but differ from the normal neutron in some other property). When matter (for example a proton) meets antimatter (for example, an anti-proton), both get destroyed - they convert to pure radiation, i.e., gamma rays. It is not currently known why there is apparently more matter than antimatter in the Universe, although it is believed that the symmetry between matter and antimatter is an almost-symmetry - i.e., the symmetry is not perfect.