Fusion with dedicated server or not ?!


I'm a bit newbie with Photon Fusion, so this might be a stupid question..;-)

I trying to create a multiplayer game, where you are multiple users to solve a task.

But where do I place my game logic ?

I would like it to be placed on the server only, and client beeing as thin as possible or should the logic be placed on each client as well ??

As I understand the server is the only one with Authority ..