The trans-Golgi network is the sorting and export region at the trans side of the Golgi apparatus. Onward traffic can supply the cell membrane, secretory granules, or the lysosome route.[ref]
The Golgi Apparatus. The Cell: A Molecular Approach, 2nd edition by Geoffrey M. Cooper; Protein Sorting and Export from the Golgi Apparatus, Figure 9.27 and lysosomal targeting discussion
Processing and sorting answer different questions. In a constructed example, two cargo proteins could receive the same carbohydrate modification yet carry different targeting information and leave in different transport vesicles. Conversely, two chemically different cargo proteins could share a destination. A processing readout alone therefore cannot establish the final address; an experiment must also identify cargo location or delivery. Return traffic and retention likewise matter: the Golgi apparatus is a working compartment, not merely a one-way queue that empties all of its enzymes into outgoing carriers.
New to topics? Read the docs here!