Program directors of radio stations report what is playing on their stations to labels. Monitoring is a system that does not rely on what the program directors or media directors says is playing. Monitoring listens to what the station is actually playing. It is a high level system and very expensive to do. The system is used mostly by medium and large record labels and implemented in several ways.
BDS (Broadcast Data Systems) - is a system that uses computers to monitor and listen to the large stations throughout the country. Subscribing customers purchase the tabulated information. They use the information to help make million dollar decisions on different markets, spins, etc.
MediaBase - is a system similar to BDS, but it uses real people to listen to what's playing. The listeners take note of special things, i.e., if the music was heard in an advertisement, the artist was mentioned by DJ and other things a computer can not report.
SoundScan - is a system for retail sales. It reports sales based on bar-code scans. Subscribers purchase the tabulated sales data to use for marketing and other purposes.
FMBQ and CMJ - are systems that use manual reporting for specialty and regular rotation charts. They are suited for the smaller label just starting out.
You should make sure you have registered your music with all of these companies so your music can be monitored as well. It will assist you in making informed decisions about your music or artists. If you are not sure how to do this, MME can assist you in making sure your products are properly registered.