Positron

Not to be confused with Electron.

Positrons are elementary particles that are like electrons, but with all opposite sign quantum numbers (including electric charge).

Positrons, like all particles, are created spontaneously from energy all the time. But they always come in matter-antimatter pairs to conserve charge, so they quickly annihilate, releasing energy. This is known happen on this very wiki! If you see a page for either of these particles, it's a virtual page in a mutual disambiguation pair, which will quickly annihilate, releasing two wikiphotons.