The Debian backports repository contain packages or newer versions of packages that did not make it into the original release. You can read more about backports on the Debian website.
To install wheezy-backports you need to either add the repository line:
deb http://http.debian.net/debian wheezy-backports main
Alternatively you can create a new sources list file with this command (run as root):
# echo 'deb http://http.debian.net/debian wheezy-backports main' > /etc/apt/sources.list.d/wheezy-backports.list
Once installed, run apt-get update:
# apt-get update
Select individual packages to install:
# apt-get -t wheezy-backports install "package"
Photo credit: Giulio Turetta