Sender Policy Framework

DNS is often shown as an upside down tree like structure, much like a family tree. The big difference is that in the DNS tree, there can be only one parent. All "family members" in the tree are called nodes.

Each node in the tree has a label.

A series of such labels form a domain.

Each node in the tree can, but does not have to, store Resource Records wherein information is stored.

The tree is divided in zones. Management of such a zone can be delegated to someone else, for instance you. All domains in such a zone are then under your control.