Dedicated servers
Photon Server is built on the concept of dedicated servers. Whereas in Unity Networking one player is the host and other players directly connect to their machine, in Photon Server you host one or more dedicated servers that players connect to. Additionally, this server usually performs as much game logic as possible, unlike Photon Unity Networking /Photon Cloud, where clients are responsible for game logic.
Dedicated servers are most often used for MMO-type games, as mentioned previously. By processing as much logic on the server as possible, the potential for cheating is dramatically reduced. For example, many MMOs implement simple point-and-click movement logic, where the player simply points where they want to move to. The client would most likely send a simple move request containing the point the user clicked. The server handles path finding and actually moving the character to that point. The client can also predict how the character will move (by generating its...