Downloaded packages

[Preston Smith]

Good morning all!

My knowledge of Linux and Kubuntu is very much a work in progress so 
many of my questions may be very basic.

Where are the downloaded package and update files stored?

After the packages have been installed or the system upgraded, can I 
safely delete the downloaded packages?  If so, how do I do this?  Can I 
set the system up so that it will delete these packages automatically 
when it is finished with them?

Is there a good tutorial which would tell me the uses of various  
sub-directories in Kubuntu so that I can understand where to look for 
various files?

Thanks for your help

Preston