We are made of stuff that we call matter. Scientists have found out that when they crash particles into one another, some other stuff is sometimes made called antimatter. This stuff has the same mass as the matter, but it has other properties that are opposite to the matter like an opposite electric charge, color charge, etc. The electron is a negatively charged particle and what we call regular matter. There is another particle with the same mass of the electron, but having a positive charge called the positron. If an electron and positron get together, they will probably annihilate. This means that they sort of cancel each other out, but their energy remains. There are antiquarks as well and they tend to annihilate with quarks except when they are in mesons. Today, there is not very much antimatter around except in mesons. It is probably because when it is created, it quickly finds matter and annihilates.