The lecture goes over some HTML tags to mark some inline text in a particular way.
You learn to mark text as being of strong importance, which by default visually appears in bold letters.
You learn to emphasize text, which by default visually appears in slanted italics font style.
The lesson also mentions how the bold tag and the idiomatic text tag were also used to visually bolden and italicize text. However today it is preferred to use the semantic tags strong and em due to their not necessarily being tied to a visual representation that could be changed. Documents can be read and understood semantically, the visual aspect being isolated from the meaning of the tags.
