What is the make.conf file? What is its purpose?
Make.conf is portage's and Funtoo's main configuration file. It contains many variables that define how a package will installed in a Funtoo system. You can customize portage internal variables, such as, portage tree location, sources tarball location, overlays, to name a few. You can customize hardware specs, such as TMPFS, disk limits, GCC compilation flags to achieve best performance, etc. A great deal of this customization is done through the make.conf file. This page will attempt to explain the uses of the make.conf file, different variables that can be added to it, and their uses.
 Where does this file reside?
The make.conf file is found at /etc/portage/make.conf and can be viewed and edited by running the following command:
# nano /etc/portage/make.conf