Business means being busy sometimes with the connotation of making money. If you need to know more precisely you might want to check the Wikipedia article on Business and please always consider viewing it from several perspectives to thoroughly understand.
these are some resources for companies or individual contractors to better understand FOSS4G business models
A listing of various studies in FLOSS and FOSS4G
- Report by e-Cology Corporation on its study of open source software (OSS) in Canada, which was contracted out by the Government of Canada
OSGeo's Service Provider Directory
In many cases Professional Support will help to speed up using and operating any kind of software environment. In some cases Commercial Services will be required to get something done in time. To make information about service providers who offer both professional and or commercial support more accessible to potential users and businesses OSGeo maintains a Service Provider Directory.
Feel free to add your Commercial Services or company to this directory or use it to search for service providers near your location or with special skills you are in need for.
OSGeo and Business
OSGeo is not a business club. Instead it aims at being a not-for-profit organization. Nonetheless a lot of the software, training and geospatial data is produced, maintained and enhanced by commercial enterprises. Services are offered around Free Software and Open Source for pay, which again is a commercial activity.
 ...which is a stupid conflict in English legal talk because obviously everybody makes a profit from OSGeo's existence.