The documentation can be written using the .auradoc file that is created every time you create a Lightning Component. The documentation for the Lightning Component is available at the https://<myDomain>.Lightning.force.com/componentReference/suite.app URL and any auradocs for custom components also appear at the same URL in your Salesforce instance. Note that <myDomain> is the domain name of your Salesforce instance.

As it currently has no documentation, you will see that the component docs for SearchApp look as follows:

Let's prettify it by adding the proper documentation. To start, let's add a description in the youtubesearch.auradoc file, as follows:

<aura:documentation>
 <aura:description>
      <p>An <code>SearchApp:youtubesearch</code> component provides a component with a search box to search across youtube</p>
   </aura:description>
   <aura:example name="ExampleName" ref=""...