<p>I keep seeing labels like below in the kubernetes yaml files that I'm trying to understand. there are certain key value pairs defined but they are defined in format</p>
<pre><code>  labels:
    app: $PROJECT_NAME-es
</code></pre>
<p>some other file</p>
<pre><code>labels:
    app: $PROJECT_NAME-some-service
</code></pre>
<p>things like this are spread all over the yaml file. each yaml file deals with one particular service and all its dependencies like service, volume claims etc.</p>
<p>I'm not an expert of kubernetes and the people around me have been using these files without modification since the creator left the company.I'm not aware if yaml files can be templates or this is something specific to google cloud where the system is hosted.</p>

Simple Fellow
<p>What it means is that the app label is parametrized. PROJECT_NAME is a variable used in the label. You need to check deployment process/pipeline on how the YAML file is getting created and deployed in kubernetes environment.</p>
