When something is openwork, the maker has left a pattern of holes in it on purpose — you can see through the gaps. The solid parts and the empty parts together make the design. Think of a wooden screen with cut-out flowers, an iron gate with curling shapes, stone carved into a lattice, or lace. People use the word for things that have been made: cloth, metal, wood, jewellery, buildings. You will meet it more on museum labels and in writing about craft or design than at the dinner table; though actually, a shop in Taiwan will often just say 鏤空 and never use the English at all. It is usually an adjective (an openwork screen), but it can also be a noun for the piece itself: a panel of openwork. It does not mean a job that is still free to take — that is a different kind of “open.”