A goal, or desired state, describes how an application should be running without prescribing every action needed to get there. You state what you want through the Kubernetes API; Kubernetes works to achieve and maintain it. section 1.0
Run an application
Creating a Deployment named kiada with the image luksa/kiada:0.1 records a goal: that container image should run in the cluster. The Deployment object is stored in the API, and Kubernetes acts on it. Reading the object back shows its current status, which may initially indicate that the application is not ready. section 3.3.1
$ kubectl create deployment kiada --image=luksa/kiada:0.1 deployment.apps/kiada created
This command creates the Deployment object that states which image should run. section 3.3.1
A goal can change. Setting a Deployment to three replicas does not tell Kubernetes to add two particular pods; it sets the desired count to three. Kubernetes compares that count with the current state and decides how to reconcile the difference. Although `kubectl scale` looks like an instruction to perform a task, it modifies the Deployment object. section 3.3.3
The scale command changes the desired replica count to three. section 3.3.3
