This video summarizes the different flavors of components in KNIME. They encapsulate a functionality, a KNIME workflow, and they have their own configuration dialogs. Components can also be used to build analytical applications on the KNIME WebPortal. Components look like KNIME nodes, and they actually are, reused locally or shared with others via KNIME Server or the KNIME Hub.
Check out the video "Sharing and Linking Components" to find out about reusing components: https://youtu.be/vt807Bg7Jag .