ZTerm is a terminal emulation program for the Macintosh. In its day, many people used it to connect to Bulletin Board Systems and download files. Now we have the internet. Its still a useful utility for those systems that only offer dialup connections and for connecting to devices through a serial port, like many routers. For newer Macintoshs that don't have a normal serial port, ZTerm can talk to ports on USB to serial adapters, through the appropriate driver software supplied with the adapter.