Default Container Objects
There are several container objects that are installed by default when you promote the first domain controller on your network. When you promote the DC, Active Directory installs for the first time, and these containers are created. They differ from manually created containers because their object attribute type is literally named a container. They don't have the same properties as other generic Active Directory containers (such as sites, domains, and OUs). You cannot delete them nor can you create new objects of that container object type. You can also not associate Group Policy Objects with these. These containers are:
Computers - All member servers in the domain are placed, by default, in the Computers container. Additionally, all workstations joined to the domain also appear in this container.
Users - Much like how Computers and Servers joined to the domain are auto-dumped into the Computers container, Users of all levels are automatically placed inside the Users container.
Builtin - Builtin does much what its name implies. It is the container that stores default groups, such as Backup Operators, Server Operators, and Group Policy Creator Owners. These groups are preconfigured with permissions to perform specific tasks that administrators will often make use of.
ForeignSecurityPrincipals - Controls and displays "trust" relationships with other domains.