mixin vs placeholder

As far as I understand, placeholder text is just light grey text inside an input field that disappears when a user clicks in the input field.

A mixin creates a breakpoint where your media will split when on different screen sizes.

Or do you mean Sass placeholders?

Having written this, I assume you mean the latter now. Mixins let you have variables. Placeholders don't. This means placeholders won't let you do context specific things the way a mixin would.

Also, so far as I understand, placeholders won't duplicate themselves since they don't compile (this is a good thing).

So there's good and bad to each.

I say this having not watched the video you come from, because the internet here is slow.

A placeholder is just an extended class, a class that isn't used except to extend in various classes..and why do you say they can't have variables?

Good article...thanks for pointing that out. Explains it well.