1. Public Updates (PUs)
Microsoft releases public updates via Windows Update each month. These updates fix security and functional problems experienced by many customers.
2. Cumulative Updates (CUs)
Then we have what are known as cumulative updates. They are also released monthly, but need to be downloaded and installed manually. They contain bugfixes reported by customers with Support Cases, along with everything else contained in the month’s PU.
3. Service Packs
Like with most other Microsoft products, there are also Service Packs containing a collection of all updates released so far, including any possible other updates.
Microsoft also releases hotfixes in irregular intervals, which rectify particularly critical problems with SharePoint components, the so-called CODs (Critical On-demand Fixes). In most cases, they are exclusively distributed by Microsoft Support and should only be installed if instructed to do so.