Save Minecraft savegame in online mode?

If i save the folder save in appdate does that also apply to the online sessions?

Want to play a game with friends but sooner or later have to reset my PC then I'm afraid that everything will be gone when I log in to those on the server: /

If it's not your server then you don't have to worry, everything will be saved on the server.

The files are all stored on the server.

Otherwise you could just edit your inventory that you have endless slides… Wouldn't you be a little stupid?