Definition of Service

• A service is a process or application that runs continually in the background. It does not display a window or have a graphical user interface (GUI) of its own.
  
  

Usage of Services

• Services are often used as part of a larger program. For example, an antivirus may use a service to monitor your computer for any signs of a virus infection. The service then alerts the central antivirus program if an infection is found, which can then perform whatever action is appropriate.
  
  

Service Hosting Instances

• Svchost.exe hosts all services running on a computer. A single svchost process may run one or more service, and there may be more than one svchost process running on a computer at once.