What it means
An eyebrow can make a concise heading easier to understand without adding more words to it. It often uses a smaller size or a different case, but its hierarchy should remain clearly secondary. On a one-page site it can also mark the transition into a new section.
Use it in practice
Use a few useful words, such as a category or an established credential. Keep the heading understandable if the label is missed.
Watch out for
Repeating the heading in smaller uppercase text adds noise. Avoid excessive tracking or low contrast at small sizes.