This manifest is used to create a deployment, which is a Kubernetes resource that manages a set of pods with the same configuration. A deployment can also provide declarative updates, scaling, and rolling back for the pods. The created pods are not receiving traffic on port 80, because the manifest does not specify a service or a selector for the deployment. A service is another Kubernetes resource that defines a logical set of pods and a policy to access them. A selector is a label query that matches the pods that belong to the service. Four pods are created as a result of applying this manifest, because the manifest specifies replicas: 4 in the spec section of the deployment

The Kubernetes object definition file is in YAML format789. Kubernetes objects are represented in the Kubernetes API, and you can express them in .yaml format7. You can execute kubectl get deployment -o yaml to get the deployment definition in a yaml format8.

To run a container in a Kubernetes environment, you should define a YAML manifest for the container and its resources2. YAML manifests are used to define Kubernetes objects, such as pods or services. These manifests describe the desired state of the system2.