Creating a good User experience will drive your product effectively to the user using it and reaching his goal. And a good UI design is a part of it. How easily the user will connect and perceive your product comes under UI. So if you are developing a website or any app it's better to have knowledge of UI/UX design. To deep dive your knowledge in this field I recommend you to go for the UI UX certification course offered by Intellipaat where they provide you with all the required skills in UI/UX designing.
Before that, watch this free tutorial video from Intellipaat if you're interested in learning more about it