The Responsive panel helps you create and manage responsive content.
Master rules
When you're editing the Master rules, any changes you make affect the entire document. Anything that isn't a CSS style override should be done within the Master rules. This means that Master rules must be selected in the Responsive panel for you to add or delete assets, components, or events.
Media rules
The Media rules section of the Responsive panel shows any vertical or horizontal ranges that you've defined by adding breakpoints. You can also define a separate set of ranges for Landscape rules and for Portrait rules when you're creating a responsive layout with dual orientation.
To add orientation rules to your media rules:
Click the orientation icon 
Breakpoints and ranges
You can add breakpoints to define new ranges, as well as view, edit, and delete existing ranges. Each range is assigned a color, and if rulers are visible, bars of those colors indicate the ranges on the rulers.
Learn more about adding breakpoints and managing ranges.