Colours, fonts, shape and a backdrop for the whole site

Look, on your site's page, changes the whole site at once. Colours: a palette of five. Type: a font pairing, and how big, how tightly spaced and whether in capitals the headings are. Shape and detail: corners, spacing, buttons (solid, outline, pill, soft or ghost), page width, the lines around things, shadows, how links in text look, how photographs are framed, and what sits between sections. Motion: how content arrives as it scrolls into view, what headings do, whether cards lift on hover, and whether a mesh backdrop drifts. Behind the whole site: a backdrop that runs behind every page. Every section follows.

Only an owner on the account can change the look. Editors can change words and pictures, and how each section and page looks. That is deliberate: the theme is the one setting where one press changes every page.