Can you brief about the Kubernetes controller manager

Multiple controller processes run on the master node but are compiled together to run as a single process which is the Kubernetes Controller Manager. So, Controller Manager is a daemon that embeds controllers and does namespace creation and garbage collection. It owns the responsibility and communicates with the API server to manage the end-points.
So, the different types of controller manager running on the master node are :
Types Of Controllers - Kubernetes Interview Questions - Edureka
Fig 9: Types Of Controllers – Kubernetes Interview Questions

Q6.  What is ETCD?

Etcd is written in Go programming language and is a distributed key-value store used for coordinating between distributed work. So, Etcd stores the configuration data of the Kubernetes cluster, representing the state of the cluster at any given point in time.