Audience design is when you create something (for example, a movie or a website) so that it appeals to a specific group of people. For example, if you wanted to make a movie that was only for children, you would design it so that it was entertaining and interesting for children - you'd have silly jokes and kid-friendly language, and maybe focus the story around a kid character. Similarly, if you wanted to create a website that had information about traveling, you would design it so that it was informative but still fun and easy-to-read, and use pictures and descriptions that would appeal to travelers.