When Active Directory is being organized and expanded, domain trees and forests will be formed. The one or more subdomains branched off of a root domain share the same namespace. In a domain tree named food.res would have branches of domains such as chili.food.res and chilis.food.res, however in the case of a domain for example sample.my created after food.res would be in a separated domain tree called sample.my. A domain is part of a separate domain tree when the domain does not contain the forest root domain or part of the parent domain.
When organizing Active Directory, multiple domain trees can be joined together to form a structure called a forest. The forest contains collections of root domains that do not share a contiguous namespace. For example the domain with the name of food.res and sample.my be part of the same forest.
The first domain name will be the forest name. For example sample.my is the first domain created, the sample.my will be the name of the forest. Later on, additional domains trees can be created in groups with different namespaces but they will all be under the sample.my forest.
A logical relationship is established between the parent and child as such they are automatically linked with trust, this provides the user on a part of the forest domain to have access towards the trusted domain’s resources.
Domain controllers are made into Global Catalog Server to enable users to find the designated resources in the forest. Within the Global Catalog Server includes information of every object in the forest, the information it contains is only there to allow the user to identify the object.