As a quick share, I have a routine of writing down the details of tasks that are accomplished, either for clients, or on my own projects.
In internet language... the term theme refers to the look and feel of a website. It's a mixture of graphics, colors, fonts, and the page layout that give a website a unique look. For example, if you think of a car... the body styling, the shape, and the colors are the "theme." The frame and engine of the car are separate, they are not part of the theme.