The Tree
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
A tree is a graph that grows from one root by branching, so exactly one path leads from the root to any other item.
Show
A tournament bracket: the championship slot is the root; every entrant starts at a leaf.
Watch for
No connection ever loops back — that single restriction is the whole definition doing its work.