Fermions , the particles that build the world, are what we call matter. Their antiparticles build antimatter. Up to date, there is no generally accepted theory why there is only matter in our world.

More about antimatter on the main page.

http://info.web.cern.ch/info/Announcements/CERN/2000/0808-ADStartUp/Story/Story-en.html#9en http://www.sciam.com/askexpert_question.cfm?articleID=000848AB-9450-1CD1-B4A8809EC588EEDF&catID=3&topicID=13

About Antimatter in German. (Antimaterie)