As a UX/UI designer, I do market research as well as quantitative and qualitative research. Using tools like Figma, I then do reports, make personas, user journeys, write summaries, and then make wireframes. I then use all of that data to design a visually appealing and user friendly layout or mockup. I follow that up with prototyping as well as user testing.
I design apps as well as responsive websites and digital products. My main job boils down to taking the idea you had and bringing it to life. I use different design tools like, for example, Figma.