The terms "remote tower" and "digital tower" are frequently used interchangeably, and in most contexts they describe the same underlying technology: air traffic services delivered from camera and sensor feeds rather than an out-the-window view in an on-airport cab. The distinction is more about emphasis and region than a hard technical line.
Remote tower emphasizes location: the controller is physically remote from the airport, often at a remote tower centre serving one or several airports. Digital tower emphasizes the technology: the reconstruction of the airfield from high-definition cameras, pan-tilt-zoom optics, and sensor overlays, whether the controller sits at the airport or elsewhere.
European programs (Sweden, Norway, Germany) tend to say "remote tower." The UK and some vendors favor "digital tower." The FAA's formal term is "Remote Tower Systems (RTS)." EUROCAE standards cover both under one framework (the ED-240 series).