The National CAD Standard is like a set of rules for designing things using a computer. It tells people who make computer designs how they should do it so that everyone can understand the design easily. It's like a special language that helps people who make different designs to understand each other better. This way, lots of people can work together and make things that look the same and work well. It's kind of like all the kids in your class following the same rules when they draw a picture, so everyone can understand what they drew. It helps everybody to work together and understand each other.