The server holds membership and roles, the project list, Planning, Rules, Activity, the questions and answers of Conversations, the project settings and your account preferences (Language, Automatic checks), what you have read, and the hosting and database passwords.
When an agent reads or writes a file or queries a database, the app on the PC only relays the call: the SyncNow server carries it out with the credentials it stores, after checking that the agent is allowed to. Earlier versions of overwritten files are kept on the SyncNow server too, not on your site or your PC.
On the PC SyncNow keeps mainly its own settings, a cache of your project list, the time it last checked for answers to the questions you asked in Conversations, and a transfer folder for files agents move with upload_path and download_path, where each session's subfolder is deleted when the session ends. A new PC therefore needs only the app and your sign-in.