partitions created/used during ubuntu install

[bruce]

Hi.

In researching ubuntu install docs, some have said/implied that the
initial partitions for install are:
 /
 /swap
 /boot

with optional being
 /home

Am I correct in thinking that the OS is basically using the top
partitions, and a reinstall/upgrade would impact these dirs.

whereas the "/home" wouldn't be touched?

I'm asking, as what happens to the /var, /etc.

IE, if once creates a webapp and uses /var/www/html/foo, should the
/var be in it's own partition?

thanks