Usability is a measure of how easy it is for people to use something, such as a website, a computer program, or a piece of equipment. When something is usable, it means that it is easy to learn, easy to use, and easy to remember how to use.
For example, if you were designing a website for kids to use, you would want to make sure that it was usable. That means you would want to make the website easy to navigate, with clear instructions and buttons that are easy to click on. You would also want to make sure that the website was visually appealing and that it didn't have any confusing or unnecessary features.
Usability is important because it makes it easier for people to use the things that they need to use in their daily lives. When something is usable, it is less frustrating to use, which can make people more likely to use it and more likely to recommend it to others.