A Short Introduction To Apt-Pinning

This article is a short overview of how to use apt-pinning on Debian
and Debian-based distributions (like Ubuntu). Apt-Pinning allows you to
use multiple releases (e.g. stable, testing, and unstable) on your system and to specify when to install a package from which release. That way you can run a system based mostly on the stable release, but also install some newer packages from testing or unstable (or third-party repositories).

Source/Kaynak : http://www.howtoforge.com/a-short-introduction-to-apt-pinning