Merge pull request #45607 from prashantrewar/update-kubectl-docs

Move the introduction page from SIG CLI guides to the kubectl reference

content/en/docs/reference/kubectl/introduction.md

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+---
+title: "Introduction To Kubectl"
+content_type: concept
+weight: 1
+---
+
+Kubectl is the Kubernetes cli version of a swiss army knife, and can do many things.
+
+While this Book is focused on using Kubectl to declaratively manage Applications in Kubernetes, it
+also covers other Kubectl functions.
+
+## Command Families
+
+Most Kubectl commands typically fall into one of a few categories:
+
+| Type                                   | Used For                   | Description                                        |
+|----------------------------------------|----------------------------|----------------------------------------------------|
+| Declarative Resource Management        | Deployment and Operations (e.g. GitOps)   | Declaratively manage Kubernetes Workloads using Resource Config     |
+| Imperative Resource Management         | Development Only           | Run commands to manage Kubernetes Workloads using Command Line arguments and flags |
+| Printing Workload State | Debugging  | Print information about Workloads |
+| Interacting with Containers | Debugging  | Exec, Attach, Cp, Logs |
+| Cluster Management | Cluster Ops | Drain and Cordon Nodes |
+
+## Declarative Application Management
+
+The preferred approach for managing Resources is through
+declarative files called Resource Config used with the Kubectl *Apply* command.
+This command reads a local (or remote) file structure and modifies cluster state to
+reflect the declared intent.
+
+{{< alert color="success" title="Apply" >}}
+Apply is the preferred mechanism for managing Resources in a Kubernetes cluster.
+{{< /alert >}}
+
+## Printing state about Workloads
+
+Users will need to view Workload state.
+
+- Printing summarize state and information about Resources
+- Printing complete state and information about Resources
+- Printing specific fields from Resources
+- Query Resources matching labels
+
+## Debugging Workloads
+
+Kubectl supports debugging by providing commands for:
+
+- Printing Container logs
+- Printing cluster events
+- Exec or attaching to a Container
+- Copying files from Containers in the cluster to a user's filesystem
+
+## Cluster Management
+
+On occasion, users may need to perform operations to the Nodes of cluster.  Kubectl supports
+commands to drain Workloads from a Node so that it can be decommission or debugged.
+
+## Porcelain
+
+Users may find using Resource Config overly verbose for *Development* and prefer to work with
+the cluster *imperatively* with a shell-like workflow.  Kubectl offers porcelain commands for
+generating and modifying Resources.
+
+- Generating + creating Resources such as Deployments, StatefulSets, Services, ConfigMaps, etc
+- Setting fields on Resources
+- Editing (live) Resources in a text editor
+
+{{< alert color="warning" title="Porcelain For Dev Only" >}}
+Porcelain commands are time saving for experimenting with workloads in a dev cluster, but shouldn't
+be used for production.
+{{< /alert >}}