Purpose of using Template types

• Template types allow you to define:

  • The resource type of the page component.
  • The policy of the root node, which defines the components allowed in the template editor.
  • It is recommended to define the breakpoints for the responsive grid and setup of the mobile emulator at on the template type. This is optional, because the configuration could also be defined on the individual template (see Template Type and Mobile Device Groups).

Please check this out.

https://experienceleague.adobe.com/docs/experience-manager-65/developing/platform/templates/page-templates-editable.html?lang=en#template-type

Before understanding the template-types, you need to understand the concept of page component/ static templates.

These are similar to those page components which are used to define the structure of the component and also define the policies, we can also configure layouts for your templates in the template-types

You create template-types only if you have different structure and different

Agenda if not one template-type can used to create multiple templates

To get more understanding on static templates please follow

https://experienceleague.adobe.com/docs/experience-manager-64/developing/platform/templates/page-templates-static.html?lang=en