Does it have a root?
A piece is rooted (有根) when a cheaper comrade protects it, unrooted (无根) when it stands alone. Attacking a rooted piece bounces off; attacking a loose one wins material. Black's horse on c7 sits on the pawn's root at c6 — but not everything in his camp is that well cared for. Hunt the piece that nobody avenges: the rooted horse can wait.