Services only started appearing in OS X, it didn't exist in any version of Mac OS before then. The difference this time is that Snow Leopard gives you much more control over the Services menu, allowing you to select which ones should be active. This, together with the tighter integration with Automator, makes it very easy to create seamless workflows, either by selecting from the Services menu, using a right-click (contextual menu) or even a keyboard shortcut.

http://www.macosxautomation.com/services/learn/tut01/index.h...

http://www.macworld.com/article/142419/2009/08/snowleopardse...