The version being run may have some outdated software, which is not in the current stable tree.
That is where backports come in.
Backports are recompiled packages from testing (mostly) and unstable (in a few cases only, e.g. security updates), so they will run without new libraries (wherever it is possible) on a stable Debian distribution.
It is recommended to pick out single backports which fits your needs, and not to use all backports available.
Example use of Backport
Pinning Backports