Modems are a peripheral which allow computers to communicate with other computers.
Wireless modems allow communication wirelessly between computers through channels.
Ender modems act as long-distance wireless modems, and are capable of cross-dimensional communications.
Wired modems allow communication through Networking Cables to other computers, and also allow long-distance peripheral usage.
The Modem (API) is the interface which is provided when one of the above modems are wrapped as a peripheral.