Q. What is the difference between Quality Updates and Feature Updates?
A. With Windows 10 and Windows Server 2016 Microsoft made a number of changes to whole the operating system is delivered and how it is patched.
Current Branch (and Current Branch for Business) was introduced as a way to update Windows 10 (and Windows Server 2016 Nano Server) every 6 months. This introduces new functionality and is known as the Feature Update.
Additionally Microsoft are moving away from releasing a large number of separate patches each month in favor of a single Cumulative Update (CU) which as the name suggests also includes all previous months updates. This is known as the Quality Update.
Therefore the Quality Update provides fixes but not new functionality while the Feature Update provides new features.