The nodes in the node tree have a hierarchical relationship to each other.
Merge with DOM - (Node) Tree
An element A is said to be preceded or followed by a second element B if A and B have the same parent node and there are no other element nodes or Text nodes (other than DOM - Text (node)) between them.
A node is the only child of an element if that element contains no other nodes other than:
- comment nodes,
- and processing instruction nodes.
The terms parent, child, and sibling are used to describe the relationships. Parent nodes have children. Children on the same level are called siblings (brothers or sisters).
- In a node tree, the top node is called the root. In HTML, it's the html element
- Every node, except the root, has exactly one parent node
- A node can have any number of children
- A leaf is a node with no children
- Siblings are nodes with the same parent