What is use case of rel attribute inside the link tag?

Question

I'm some HTML templates, there were link tags used for linking CSS files. In those tags, 'rel' attribute is used. But, in all those links, rel is same.
rel="stylesheet"
https://code.sololearn.com/WlUahGUylFpO/?ref=app

Answer 1

it gives the link a definition for what is being used. in your case, rel="stylesheet" is defining what the link is actually linking to, CSS.

Answer 2

{{{
it gives the link a definition for what is being used. in your case, rel="stylesheet" is defining what the link is actually linking to, CSS.
}}}

Is that necessary to specify that attribute?
How that attribute helps in the code?