Working is a state, not a type. A displayed limit, a hidden-order, an untriggered stop-order held at the broker and the unexecuted remainder of a partly filled order are all working.
The reason to track the state carefully is that working orders are live exposure. A forgotten stop that survives after you flatten manually can open a brand new position in the opposite direction.
Example: you are long 400 shares with a stop-sell at 48.00 and a take-profit sell at 52.00, both working and not linked as an oco-order. The stop fires and you are flat. The sell at 52.00 is still working; a rally to 52.00 fills it and leaves you short 400 shares you never intended to hold.
Related: resting-order, oco-order, order-expiry, flatten