Each package is classified as one of three different types. Security updates are those which fix a discovered security vulnerability. You should always install security updates.
Bugfix updates solve problems discovered with the distribution.
Lastly, package enhancement updates are not critical but do improve or enhance your Yellow Dog Linux operating system. Several problems created the potential for users to gain root access. Fixed a problem that could allow a user to overwrite any file on a system. Fixed a problem allowing console users to get root access. Fixed a problem with URL handling.