Describe what a “reset” CSS file does and how it's useful. Are you familiar with normalize.css? Do you understand how they differ?

Resets are so wildly common in CSS that anyone who is a front end developer type has surely used them. Do they do so blindly or do they know why? The reason is essentially that different browsers have different default styling for elements, and if you don't deal with that at all, you risk designers looking unnecessarily different in different browsers and possibly more dramatic breaking problems.
Normalize you might call a CSS reset alternative. Instead of wiping out all styles, it delivers a set of reasonable defaults. It doesn't unset things that are already consistent across browsers and reasonable (e.g. bold headers). In that way it does some less than a reset. It also does some more than a reset in that it handles quirks you may never consider, like HTML5 audio element inconsistencies or line-height inconsistencies when you use sub and sup elements.