Check out a free preview of the full Responsive Typography course:
The "Polish" Lesson is part of the full, Responsive Typography course featured in this preview video. Here's what you'd learn in this lesson:
Opentype fonts provide extra features that are available in the browser. For example, turning on ligatures adds a nice finishing effect to headings or other prominent text. Some features do add extra file size or download time so web designers still want to keep performance in mind when adding polish.