So they are both objects that you use to organise other objects. You can add users, groups and computers to both of them.
- What is the difference between them?
- What is the best way to divide users and computers of different departments in a company (OU or Groups)?
Summary:
OUs contain user objects, groups have a list of user objects.
They're like folders (OU) and files (groups) on a file server (your AD): it is easier to manage permissions/ACLs on whole folders instead of single files, and let them be applied to the files (groups) by inheritance automatically. This analogy is explained in detail in Access Denied: Understand the Difference Between AD OUs and Groups:
Differences:
Recommendations:
So you should use them both to do different things.
Generally use OUs to organise your active directory tree and apply group policies.
Use groups for security by giving them permissions to resources, and then add users to them.
Groups are for granting access to data and organizational units (OUs for short) are for organizing and controling objects (users and computers) via delegation and group policy settings.
This depends on your organizational fancy. How you want to logically organize your network.