The idea is that the "makers" are "offering liquidity" with their orders (offers is probably a better word than orders here). They are publishing these offers. The takers then come along and ... take these offers They do that by private messaging to the makers to request the initiation of a coinjoin transaction. After an initial "handshake", this communication is E2E encrypted. The intended result is that the taker (who's paying the fee) is getting maximal privacy. No one else (including the makers) knows which output corresponds to the taker's input, assuming more than one maker is involved (notice: in a 2 party coinjoin, there is *no* cryptographic magic trick that can prevent your counterparty from knowing your output - it's the one that isn't his!).