Spacer components are used to add vertical spacing between elements. On the web we would achieve this by setting bottom margins, but this rarely works in email clients.
Drag and drop a
Spacer component from the Component panel to the stage.
When you select it, in the Appearance panel you can change its height and background color.
Spacers are just tables with a fixed height. You can make them responsive by setting different heights on mobile and desktop, or by showing and hiding themwith the Conditional Visibility options.