Note : kubectl is a command-line tool tool that allows you to run commands against Kubernetes clusters

In order for kubectl to find and access a given kubernetes cluster, it needs kubeconfig file for a given K8s cluster you want to connect with (if you dont have one you can install a local cluster to play with using something like K8s Minikube which will then give you this file to connect to minikube)

If you already have a cluster then check that kubectl is properly configured use kubectl cluster-info command , if it is not you will receive below error log.

$ kubectl cluster-info

To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
The connection to the server localhost:8080 was refused - did you specify the right host or port?

So to connect to a cluster you want work toward using kubectl you need to find kubeconfig file and configure the environment variable to point to it. Meaning if your $HOME/.kube/config file is not already listed in your KUBECONFIG environment variable, fix your KUBECONFIG environment variable by export KUBECONFIG=$KUBECONFIG:$HOME/.kube/config to point to correct kubeconfig file to be used.

Once you have right kubeconfig exported cluster-info command should load the details as below

$ kubectl cluster-info

Kubernetes master is running at https://xx.xx.xx.xx:6443
KubeDNS is running at https://xx.xx.xx.xx:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

As you mentioned you have installed kubectl - command-line tool, which allows you to run commands against Kubernetes clusters. You can use kubectl to deploy applications, inspect and manage cluster resources, and view logs.

However to kubectl could run any command you need to have a cluster.

The most common is Minikube. However, you will need a hypervisor as Virtualbox or Hyperkit. You also should read about Docker Desktop on Mac.

If you will search for more information you can find that people also using Kubeadm but its not supported on MacOS.

It was mentioned in another StackOverflow question, you can find it here.

kubectl version prints out both the client version and server version. To fetch the server version, it connects to kubernetes api server. You either do not have the cluster installed or have not configured your kubectl properly to communicate with the remote cluster. So it is only printing client version and throwing an error for server version.

Sample output:

# kubectl version
Client Version: version.Info{Major:"1", Minor:"13", GitVersion:"v1.13.5", GitCommit:"2166946f41b36dea2c4626f90a77706f426cdea2", GitTreeState:"clean", BuildDate:"2019-03-25T15:26:52Z", GoVersion:"go1.11.5", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"13", GitVersion:"v1.13.5", GitCommit:"2166946f41b36dea2c4626f90a77706f426cdea2", GitTreeState:"clean", BuildDate:"2019-03-25T15:19:22Z", GoVersion:"go1.11.5", Compiler:"gc", Platform:"linux/amd64"}

You can use kubectl version --client to get only client version.

# kubectl version --client
Client Version: version.Info{Major:"1", Minor:"13", GitVersion:"v1.13.5", GitCommit:"2166946f41b36dea2c4626f90a77706f426cdea2", GitTreeState:"clean", BuildDate:"2019-03-25T15:26:52Z", GoVersion:"go1.11.5", Compiler:"gc", Platform:"linux/amd64"}