Implementation in Mac OS
On the original Mac OS, optional features and services were provided by files loaded at startup time that patched the operating system; these were known as system extensions and control panels. Later versions of classic Mac OS augmented these with fully fledged faceless background applications: regular applications that ran in the background. To the user, these were still described as regular system extensions.
OS X, which is a Unix system, has daemons. There is a category of software called services as well, but these are different in concept from Windows services.
Read more about this topic: Daemon (computing)