Linux/Unix folder paths

[Sarah Reichelt]

Hello all you Linux/Unix gurus out there,

I was hoping someone would be able to tell me a few things about where 
such systems put various types of files.

Where so you store preferences? I see that the specialFolderPath() 
function is Windows & Mac only, so how would I know where to store 
preferences on a Linux system?

Where should an application be installed? And what if I want the 
application to be available to a particular user only e.g. on my Mac OS 
X system, I have /Applications for apps that everyone can use and 
/Users/sarah/Applications for apps that only I can use. The second is 
better if I need to write to the application folder as the user has 
write access to that folder even if not an admin user (at least I think 
that is correct).

TIA,
Sarah