We can store your component’s template in one of two places. We can define it inline using the template property, or we can define the template in a separate HTML file and link to it in the component metadata using the @Component decorator’s templateUrl property.
The choice between inline and separate HTML is a matter of taste, circumstances, and organization policy. But normally we use inline template for small portion of code and external template file for bigger views. By default, the Angular CLI generates components with a template file.