Each distro is supported for a certain length of time after release. During this period developers provide security updates and bug fixes, also called patches. These updates can be installed via the built in program installer for a Linux version, or through a command such as "yum update".
LTS (Long Term Support)
Some developers produce a version with an extended support window. This LTS type distro allows people to keep things secure for longer without re-installing. A few have around a 10 year update cycle, which means a nice long stretch before being compelled to upgrade by security necessity.
Rolling releases are continuously updated, as opposed to using a strict numbered software versioning system. Updates are deployed based upon need, or to test new features. Some distos such as Gentoo use this primarily, and others mainain both a standard release branch and a rolling release one for development.
A patch is a piece of software designed to update a computer program or repair potential issues. This includes improving usability or performance, and fixing bugs.
Patch management is the process of using a strategy and plan of what patches should be applied to which systems at a specified time.