Loading fonts has one of the largest impacts on page performance. Fonts are usually loaded in CSS or ahead of your HTML before other, more critical, assets. This optimization loads fonts after other page resources.
Loading fonts after other resources means that text and images are shown to the user earlier. This improves both FCP and LCP scores.
Fonts may be used for purposes other than just styling text, such as using them for icons like FontAwesome. Deferring these critical resources may result in flicker.
Best practice is to use this option in conjunction with other options such as font_display and font_map to ensure correct functionality. Likewise, for icon fonts it’s better to use the individual image files as needed instead of including the entire font file (which has a lot of unneeded content).