The em element adds emphasis. It can change the meaning of a sentence.

<p>You should <em>always</em> wear a helmet.</p>

Browsers display em as italic by default, but the meaning matters more than the style.

The strong element marks serious importance, urgency, or warning:

<p><strong>Do not leave your bicycle unlocked.</strong></p>

Browsers display strong as bold by default.

HTML also has i and b. They do not mean exactly the same thing:

em is stress emphasis
strong is importance
i marks text set apart from normal prose, such as a foreign phrase or technical term
b draws attention without adding importance, such as a keyword in a summary

Ask what the text means before choosing the element. If you only want italic or bold styling, CSS is usually the right tool.

Quick check

Result

You got of right.