User experience (or UX) design is a web design methodology that focuses on how the user interacts with, engages, and behaves on the site. Proper UX design uses real data to steer the evolution of the site and can often involve an element of A/B testing to identify optimal design options, layouts etc
Some types of user behaviour that search engines collect include click-through rate (CTR), navigational paths (the journey of the user through the website), time on site, duration on page, frequency of visits and so on. We discuss user behaviour data in more detail in another post.
It means that web design is on Google's radar. It stresses the importance of good UX design and optimisation techniques such as A/B testing. The result is even greater rewards for investing in proper technical, strategic and creative skills which usually means a better return on your investment.
Search visibility is always going to be based on search engines interpretations, not subjective user feedback so there needs to be a careful balance introduced where we worship at the altar of Google but also ensure high engagement from real-life users. These do not always go hand-in-hand.