By default the Total theme icons load as a custom font family. The theme uses a font-family by default because it provides better consistency with spacing and line-heights, however, it’s possible to instead use SVG’s for your site so that the theme icon fonts aren’t all loaded on every page which can slim down the site a little and is something you may want to enable if you aren’t using many icons on the site or are trying to optimize the site to the fullest.
Simply go to the main Theme Panel and from here enable the option that reads “SVG Theme Icons“.