From the article:

Do not confuse the <b> element with the <strong>, <em>, or <mark> elements. The <strong> element represents text of certain importance, <em> puts some emphasis on the text and the <mark> element represents text of certain relevance. The <b> element doesn't convey such special semantic information; use it only when no others fit.

Before this unusual rebranding, we had <strong>, another ridiculous attempt to add some kind of semantics (despite being essentially meaningless) to the <b> element, created during the insane excesses of the XHTML STRICT era.

<b> was, is, and always will be the bold text element. No one is going to die if there is some slight semantic meaning in your HTML.

I've always known it to be:

<b> and <i> for font manipulation (bold and italics)

<strong> and <em> for giving text importance (important and emphasized)

but honestly, I don't think it matters as long as you're consistent.

I always thought the B stood for bold. But it is really bring attention to?