🌳 In Microsoft Active Directory, forests and trees are part of the logical structure used to organize and manage network resources across large organizations.

🌲 What Is a Domain Tree?

A domain tree is a collection of one or more domains that share a contiguous namespace:

• Starts with a root domain (e.g., contoso.com)
• Child domains inherit the parent’s name (e.g., sales.contoso.com, hr.contoso.com)
• Domains in a tree automatically trust each other via transitive trust

Think of it like branches growing from a single trunk—each domain is a branch, but they’re all part of the same tree.

🌳 What Is a Forest?

A forest is a collection of one or more domain trees that:

• Share a common schema, global catalog, and directory configuration
• May have different namespaces (e.g., contoso.com and fabrikam.net)
• Are connected by trust relationships, allowing resource sharing

Forests are the top-level security boundary in Active Directory. Admins in one forest can’t access another forest unless a trust is explicitly established.

🧠 Visual Analogy

Imagine a forest with multiple trees:

• Each tree has its own root and branches (domains)
• The forest connects all trees under one ecosystem (shared schema and configuration)

🧪 Real-World Example

A company acquires another business:

• Original company uses contoso.com with child domains like sales.contoso.com
• Acquired company uses fabrikam.net
• Both trees can be joined into a single forest to allow collaboration while maintaining separate namespaces