I downloaded stage3 tarball for amd64 from gentoo download page. The file contains image of root file system.I was expecting an iso file because the handbook doesn't talk about this file. It says I am supposed to burn .iso into a CD and boot into it. But the gentoo servers don't have any iso file in the directory mentioned by the manual page.  FAQ page doesn't have question regarding this either. any input from experienced user would be appreciated. Thank you.
got a .tar.bz2 file for gentoo installation. Expecting .iso file
system installation;gentoo