The fundamental particles that make up our world have a number of characteristic properties that can be measured in the laboratory. Examples of the particles would be electrons, positrons, protons, neutrons, a variety of mesons, etc. For some of the properties, like electric charge, so-called 'color', 'charge conjugation', etc, the algebraic sign of the anti-particle changes. For other properties, for example mass, angular momentum, and lifetime, the value is the same for particle and antiparticle.
The most spectacular thing is that if a particle meets up with its antiparticle partner... Kablooie. They mutually annhilate and give off radiation of various sorts. Energy is conserved, of course.
(published on 10/22/2007)