Model-driven PowerApps allows creating component-focused Microsoft PowerApps. Also add the general [powerapps] tag and [dynamics-crm] to your question.
Model-driven PowerApps is a component-focused approach to Microsoft PowerApps. Compared to Canvas Apps where the designer has full control over the layout of the app, with model-driven apps a great part of the layout is determined and largely defined by the components you add to the app.
Dynamics CRM SMEs will be able to help answering the questions in Model driven powerapps, as the core SaaS product is the same.