What does the letter C refer to in Type-C? What Types are used by my other devices (e.g., computer, printer, phone, etc.)?

The C refers to the connector style. Type-A connectors are the traditional rectangular plugs that we're all familiar with. Type-B is an older device-side connector, which is often used by printers, scanners, etc. Older mobile devices use the Mini Type-B connector, while most new devices use the Micro Type-B connector.