You design the layout or front end of a website based on customer requirements.
You pay mind not only to aesthetics, but also functionality and user-friendliness.
You design the displayed content in an attractive manner by selecting colors, layouts, and fonts and working with various media such as text, graphics, video, etc.
You often create several design options to present to clients, who then select the final design.
You determine the content structure of the website, meaning, the navigation structure and the links between the individual pages.
You arrange for the technical implementation as soon as the design has been approved by the client.
Depending on the project and technologies required, the technical implementation may fall under your purview or be taken over by a web development team.