Container components are the building blocks of your website and they are very versatile. They can be used as a background, design elements or to keep other components together. If you look carefully at the components used in the template you selected, you'll notice it contains a lot of container components.
There are two types of containers:
The Strip component always stretches over the whole width of your site. It is convenient as a background or banner but also allows you to pin a group of components to the top/bottom of the page or add scroll effects.
The Box component is used to group other components together, allowing you to make sure these components also stick together in mobile view. You can also use it as a background or make it into a circle by rounding the corners.