The objects in the Kubernetes system are the entities that represent the status of a cluster. They can specifically label:
The executed applications and tell about nodes
Available resources
Guidelines for the behavior of the applications, such as Reboot policies, fault tolerance, and upgrades.
YAML stands for Yet Another Markup Language and is a readable, text-based format for postulating the type information (configuration). To know more about the Kubernetes objects and YAML file, do watch the below video on Kubernetes Architecture: