Why there are 2 <link> tags in html head elements?

In this interactive lesson (URL=https://www.codecademy.com/courses/learn-css/lessons/box-model-intro/exercises/box-model-intro), I noticed there are 2 tags in html head elements, and the the first one only have two attributes instead of three: href and rel.

Why is the first one necessary? Why is type attribute missing in it?

P.S. I opened the URL link in another browser tab, only being shown with a plain webpage written with pure text code-like lines.

source: but given that CSS is the only stylesheet language used on the web, not only is it possible to omit the type attribute, but is actually now recommended practice.

but i believe this is the case since html5, before (html4 and earlier) type was required.