https://w3c.github.io/csswg-drafts/css2/#inline-boxes
An inline box is one that is both inline-level and whose contents participate in its containing inline formatting context. A non-replaced element with a display value of inline generates an inline box. Inline-level boxes that are not inline boxes (such as replaced inline-level elements, inline-block elements, and inline-table elements) are called atomic inline-level boxes because they participate in their inline formatting context as a single opaque box.
I quoted the specification but I don't understand the part marked in bold.
Could you give me an example of inline box
and an example of something that is not inline box
?
I especially need details of the part marked in bold, please.