Migrating Grails 2.X to 3.X - What are Profiles?

I am a rather novice programmer and I have been learning Grails 2 and 3. For my work, I have been assigned to migrate Grails 2 applications to Grails 3. I do not want to just simply follow a copy-paste tutorial and not develop any depth of knowledge as a result.

Currently, I have been running alongst these links that detail the migration process:

• https://docs.grails.org/3.0.x/guide/upgrading.html
• https://opensource.com/article/18/5/upgrading-grails-applications
• The above link from opensource points to https://docs.grails.org/latest/guide/profiles.html for further detailing on profiles. However, I do earnestly do not understand a majority of its intricacies.

The second link that elaborates more on the original Grails migration documentation elaborates more on the topic of profiles but I feel as though I'm not acquiring the big picture element here. Are profiles essentially different templates to utilize for YAML files? For instance, currently my applications utilize a web profile as "application.yml."

Are profiles essentially different templates to utilize for YAML files?

No.

A profile represents a type of application. For example, we have a web profile for traditional web applications which do server side HTML generation, we have a react profile that contains a rest backend and a React based SPA front end, we have a rest-api profile which is populated with sensible defaults and dependencies for publishing REST apis, etc.

It is not the case that profiles are essentially different templates to utilize for YAML files. YAML files are 1 tiny piece of profiles.