Comment tree
Comments are arranged in a tree structure
The term comment tree, also called comment thread, means that comments are organized in a tree structure, so that comments can have children — which we call replies.
For example:
root comment A
+-- child comment A1
+-- child comment A2
root comment B
+-- child comment B1
+-- child comment B11
+-- child comment B2
+- child comment B21
+- child comment B22
...
Every child comment can, in turn, also have children (replies), and so on.
Every domain page has an own comment tree.