Whatever type of web presentation you are making you are going to use some type of web development tool. Yes, you will have to have that tool work for all devises. At some point, you may need or want to adjust some settings to change the appearance of the presentation. Hence, it will be helpful to understand things about CSS and media queries.
In this short video, you can get a summary of what is going on with responsive web design basic code. There are three short videos in this part of the Bill the Geek, Adobe Dreamweaver CC video series covering responsive web design code at very basic, but extremely important code issues in this matter of web design.
Part 2. What is a CSS Media Query?