Updates are considered by convention to be installation of patches and fixes to currently installed packages within the same release level. This is separate and distinct from an upgrade which is upgrading from one release level of a distribution to another, such as from Fedora 16 to Fedora 17.
Updates can be performed in several ways, but the method I recommend for administrators is to use YUM, Yellow Dog Updater Modified. Using YUM to update from the command line looks like the following command which will update every RPM package in your defined and enabled repositories without the need for any intervention.
yum -y update
The -y option indicates that any “yes|no” questions posed by YUM will be automatically answered with “yes”.