What is the difference between a PU, a CU and a COD?

As per Stefan Goßner’s latest blog post update good description of the difference between SharePoint CU, PU and COD and recommendations for when they should be installed.

Below is the URL:

https://blogs.technet.microsoft.com/stefan_gossner/2013/03/21/common-question-what-is-the-difference-between-a-pu-a-cu-and-a-cod/