Domain and workgroup

hi
Can any one explain and tell me the main difference between Domain and workgroup?

the most essential is that global policies and better mangmet of comp can be done with domain. in workgroup this does not apply.

by experts domain is considered a patch to the operating systems.

regards

Also with a domain the security (user logon access and rights of access to network resources) are enforced centrally by the domain controller, while with a workgroup every participating machine has to be set up individually for these things