<p>I have a deployment, that looks as follows: 
<a href="https://i.stack.imgur.com/j5TPW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/j5TPW.png" alt="enter image description here"></a></p>

<p>The question is, what is the difference between the red border label and the violet one? </p>

softshipper
<p>These key fields are refereed as Labels on Kubernetes. These labels are used in Kubernetes in order to organize our cluster. </p>

<p>Labels are key/value pairs that are attached to objects that can be used to identify or group resources in Kubernetes. They can be used to select resources from a list. </p>

<p>Labels can be attached to objects at creation time and subsequently added and modified at any time. Each object can have a set of key/value labels defined. Each Key must be unique for a given object.</p>

<p>Going deeper on it, lets suppose you have this Pod in your cluster:</p>

<pre><code>apiVersion: v1
kind: Pod
metadata:
  name: sample-pod
  namespace: default
  labels:  
    env: development
spec:
  containers:
  - name: busybox
    image: busybox
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
</code></pre>

<p>As you can see we are setting one label: <code>env: development</code></p>

<p>If you deploy this pod you can run the following command to list all lables set to this pod: </p>

<pre class="lang-sh prettyprint-override"><code>kubectl get pod sample-pod --show-labels
NAME         READY   STATUS    RESTARTS   AGE   LABELS
sample-pod   1/1     Running   0          28s   env=development
</code></pre>

<p>You can also list all pods with <code>development</code> label:</p>

<pre><code>$ kubectl get pods -l env=development
NAME         READY   STATUS    RESTARTS   AGE
sample-pod   1/1     Running   0          106s
</code></pre>

<p>You can also delete a pod using the label selection: </p>

<pre><code>pod "sample-pod" deleted
</code></pre>

<p>Matching objects must satisfy all of the specified label constraints, though they may have additional labels as well. Three kinds of operators are admitted  <code>=</code>,<code>==</code>,<code>!=</code>. The first two represent  <em>equality</em>  (and are simply synonyms), while the latter represents  <em>inequality</em>. For example:</p>

<pre><code>environment = production
tier != frontend
</code></pre>

<p>You can read more about labels on <a href="https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/" rel="nofollow noreferrer">Kubernetes Documentation</a>.</p>
