Templates (Twig) 

OroPlatform-based application uses the Twig templating engine to render the content.

See the detailed documentation in:

Find Twig Templates 

To find the Twig template file and Twig block that is used for rendering specific block of a content, you can use Twig Inspector. The inspector enables you to navigate instantly from a Browser to the Twig template that opens automatically in a PhpStorm.

Override Twig Templates 

You can override one of the platform templates by adding a template to the same path under templates/bundles. For example, to override the Grid/widget/widget.html.twig template from the DataGridBundle, create a new template file located at templates/bundles/OroDataGridBundle/Grid/widget/widget.html.twig.