My one month of the trial is over and now I can not use ther server function . But I dont know what is the serverfuntion? I can switch my PC on and off in my house and from my working place.  Why or when do I need the server thing?

The 'Server thing', is for a Windows File Server (Windows 2003, 2008, 2012 and Windows SBS 2003, 2007 + 2011). Mainly for an office environment