Windows Services are applications that typically start when the computer is booted and run quietly in the background until it is shut down. Strictly speaking, a service is any Windows application that is implemented with the services API. However, services normally handle low-level tasks that require little or no user interaction.
Although services are often effectively invisible to users, Windows cannot function normally without them. A number of essential operating system functions are handled by services, including Networking, Hardware and Remote access.
In addition to services that are part of Windows, most computers also have several third-party applications that run partly or wholly as services. Common examples of third-party services include firewalls and antivirus applications.
This white paper from Microsoft provides an overview of the changes to the services model that were introduced beginning with Windows Vista and is also applicable to Windows Server 2008 R2 and Windows 7. You can also learn more about svchost.exe here.
It covers the following topics:
- How Services Work
- Changes to the Windows Services starting with Vista
- Security Enhancements to Windows Services
- Running with Least Privilege
- Service Isolation
- Restricted Network Access0ry
- Session Isolation
- Performance Enhancements
- Delayed Auto-Start
- Service State Change Notifications
- Other Enhancements
- Preshutdown Notifications and Shutdown Ordering
- Failure Detection and Recovery
It also provides some best-practices guidelines for developers who intend to implement services for these versions of Windows.
You can download the whitepaper from Microsoft.
Incidentally, Microsoft has made some changes to the way Services are run in Windows 8, you can read more about it here.
SMART, the Windows 7, Vista, XP Services Tweaker is a freeware utility which helps you tweak Windows 7 Services, based on the suggested configurations of BlackVipers and also lets you reset Services values to its defaults. You may want to check it out!