what is update domain and fault domain in azure

Question

Also, I want to know how they are connected to the availability sets.

Answer 1

Every availability set has two parts to it - Update domain and fault domain.

Fault Domain is a collection of a server, network and storage resources.

Update Domain ensures that Azure performs it's software updates from time to time. The resources are isolated. 

To learn more about these resources, check this azure training out!