You’re currently using the System Stack fonts, which are the local browser fonts, these are:
font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
All about font properties here:
https://www.w3schools.com/css/css_font.asp