What is the alternative or equivalent to Windows services on Gnu/Linux?

Question

I was wondering what is the alternative or equivalent to Windows services on Gnu/Linux. Is it a sever like X or Pulseaudio but that wouldn't make any sense because the theme service on windows, a alternative to that on Gnu/Linux would be a WM, or a DE. Is it like the Windows registry when there isn't truly a alternative or a equivalent to it other then the your home user directory.

Answer 1

as I mentioned in the comment:

as Wikipedia link mention: In Windows NT operating systems, a Windows service is a computer program that operates in the background.[1] It is similar in concept to a Unix daemon.

A daemon is a type of program on Unix-like operating systems that runs unobtrusively in the background, rather than under the direct control of a user, waiting to be activated by the occurance of a specific event or condition.

On the Microsoft Windows operating systems, programs called services perform the functions of daemons, although the term daemon is now sometimes being used with regard to those systems as well.

source: http://www.linfo.org/daemon.html

UPDATE( More details and actual comparison):

1. • UNIX: A daemon is a process that detaches itself from the terminal and runs disconnected in the background, waiting for requests and responding to them.
     
   • Windows: A service is a special type of application that is available on Windows and runs in the background with special privileges.
2. • In UNIX, a daemon is a process that the system starts to provide a service to other applications. Typically, the daemon does not interact with users. UNIX daemons are started at boot time from init or rc scripts. To modify such a script, it needs to be opened in a text editor and the values of the variables in the script need to be physically changed. On UNIX, a daemon runs with an appropriate user name for the service that it provides or as a root user.
     
   • A Windows service is the equivalent of a UNIX daemon. It is a process that provides one or more facilities to client processes. Typically, a service is a long-running, Windows-based application that does not interact with users and, consequently, does not include a UI. Services may start when the system restarts and then continue running across logon sessions. Windows has a registry that stores the values of the variables used in the services. Control Panel provides a UI that allows users to set the variables with the valid values in the registry. The security context of that user determines the capabilities of the service. Most services run as either Local Service or Network Service. The latter is required if the service needs to access network resources and must run as a domain user with enough privileges to perform the required tasks.