The FlowType widget uses FlowType.js to adjust font sizes automatically based on screen width. As a page (or element) gets narrower, the font gets smaller. As the page gets wider, the font gets bigger.
To create a similar behavior without FlowType, you’d have to create manage several media queries.
Instead, with FlowType create maximum and minimum thresholds, so the font won’t get too small or too big. And then you let visitors’ screens determine the exact font size.