Text formatting tags give text visual styling or added meaning.
<b>— purely visual bold<strong>— bold that carries importance<i>— visual italic<em>— italic that carries emphasis
If you care about accessibility and SEO, it's better to use <strong> and <em> where they actually fit.
html
<p>This is a <b>bold</b> word.</p>
<p>This is <strong>important</strong> text.</p>
<p>This is an <i>italic</i> word.</p>
<p>This is <em>emphasized</em> text.</p>You should see
You should see paragraphs containing bold/italic text.