Usability on websites refers to the user-friendliness and functionality of a website. A website with good usability is easy to navigate, the information is easy to find and understand, and users can easily achieve their goals on the website. This also means that the website loads quickly and displays well on different devices and screen sizes. Good usability is important as it ensures that users are happy to stay on the website and will return. Poor usability, on the other hand, can lead to users quickly leaving the website and looking elsewhere.