Just as the underlying system packages are updated, Digium releases updates to Asterisk whenever necessary in order to fix bugs or patch security concerns. If Asterisk was installed from source, it will not be updated when the system packages are updated. Updating Asterisk versions is very similar to the process of installing Asterisk.
Note that "updating" Asterisk in this context means to update Asterisk to a new release of the same major version that is currently running (for example, updating from 1.4.22 to 1.4.24). It does not mean updating between major release versions (for example, 1.4 to 1.6). Major version upgrades may be required during the life of a PBX, but these types of upgrades require special planning due to new features or features that may be deprecated or non-existent in the upgraded version (causing Asterisk to stop routing calls properly).
In order to make upgrades simple, Digium uses files that have the major version number suffixed with...