着 indicates a continuous state (not an action in progress like 在). Compare: 门开着 (the door IS open — state) vs. 他在开门 (he IS opening the door — action in progress).
mistakes
着 has multiple pronunciations: zhe (particle for ongoing state), zháo (to touch/catch), and zhāo (a move in chess). The particle zhe is by far the most common.
