Continuous state with 着

着 is a particle that explicitly marks that an action is ongoing. It’s not used nearly as much as 在 is in everyday speech, though.

First, you can use it after a verb to show that something is in the continuous state expressed by that verb.

The restaurant’s door is open.

Remember, this is different than the “change of state” particle 了. Note the difference:

The restaurant’s door is now closed.

Another common verb you see this particle with is 关 “to close.”

The car’s windows are all closed.