Grayware refers to applications or files that are not classified as viruses or Trojan horse programs, but can still negatively affect the performance of the computers on your network and introduce significant security risks to your organization. The best example are the annoying pop-ups that come up when you open your browser. In addition they also computers vulnerable to attacks.
Other examples are spyware, adware, dialers, joke programs, remote access tools, and any other unwelcome files and programs apart from viruses that can harm the performance of computers on your network.