Contesting (also known as radiosport) is a competitive activity pursued by amateur radio operators. In a contest, an amateur radio station, which may be operated by an individual or a team, seeks to contact as many other amateur radio stations as possible in a given period of time and exchange information.
DXCC
The ARRL has created a contest that requires the amateur radio operator to provide 100 confirmed contacts, each in a different country. The ARRL DX Century Club page has all of the details you need to start working on this certificate.