In terms of web development, usability is about how easy it is to use and interact with the website.
Main Components of Usability
Good Navigation
Every website has hundreds of pages with different kinds of information from their products to the brand’s story. Users land on different pages and it should be easy for them to move to any other page from there.
Performance
Visitors are unlikely to wait for more than 3 seconds for the website to load. The preferred loading time is under a second, according to both users and search engines. By the way, the latter takes into account the website performance while ranking search results. You can reduce the loading time by choosing the right host, image size optimization, decreasing the number of plugins used, or using website caching.
Readability
Most of the pages have some kind of text on them and it better be readable enough. Therefore, make sure that the font is not fancy in an unreadable way, text color is appropriate and creates good contrast with the background, and the size of letters is optimal too.
Responsiveness
The website should have both desktop and mobile versions and open the right one based on what device the visitor is using. It is an important part of usability since more than half of traffic is coming from mobile devices nowadays. Responsive designs are easy to create, you may even use a plugin that will do all the job for you.