Remedy Action Request System is a client-server software application toolset. It is most commonly used as a tracking system. It can use diffrent databases for storage of data and logic. The server run on many diffrent operating systems.
Remedy Corp. was once a the company that created Remedy Action Request System. In 2001 Peregrine Systems bought Remedy Corp. But after Peregrine Systems had some problems with there accounting the Remedy part was, in 2002, sold to BMC Software.
Remedy Action Request System is a platform for making application. But BMC also delivers already functional application to us. That means you do not have to develop your own applications. Of curse there are other companies that also delivers ready to use applications.