The Full Form of YUM is‍ Yellowdog Updater, Modified.

Yellowdog Update, Modified (YUM) is a program that manages installation, updates and removal for Red Hat package manager (RPM) systems. YUM allows the user to update groups of machines without having to update each RPM separately.

A package manager is a program that automates installation, management and removal of software packages. Because some Linux distributions and other Unix-derived operating systems consist of thousands of software packages, package management systems are crucial.

Yum is essentially a package manager for RPM (which is, itself, a package manager). RPM works on the level of single packages and is not concerned with any dependencies. YUM computes dependencies for RPM and takes any actions required to successfully install software packages. Because YUM automatically locates and obtains the correct RPM packages from repositories, the user doesn’t have to manually find and install new applications or updates. The user can update all system software with a single command or search for new software by specifying criteria.

Other features of the YUM package manager include:

• Simple interface.
• Multiple repositories.
• Simple config file.
• Fast operation.
• RPM-consistent behavior.
• comps.xml group support, including multiple repository groups.