This animation shows you how choosing a template brings you shapes automatically.
One way to get shapes is to choose a template. A template is one of the drawing type options you see when you start Visio. When you choose a template, the stencils and shapes for that template will appear in the Shapes window, ready to work with.
Click the Play button to see this process of choosing a template.
At the end of this animation you see the Shapes window, with the names of stencils near the top and the shapes for one of those stencils below the names.
The advantage of using a template is that it provides you with lots of shapes organized for a specific purpose and related to each other. In this example, the shapes are specific to flowcharts. If you chose another template, you'd get shapes designed and organized for that template's purpose instead.