I call rem , the root em. Assuming the “r” comes from the word, “root”. While this may not be the general way people describe the rem unit, it will help you form great mental models.

The em unit scales against the font-size of the parent element, BUT the rem unit will only scale against the root element.

The root element here is usually, the html element.

Let’s see an example:

If you wrote this:

Get hands-on with 1200+ tech skills courses.