Family
      @font-face {
        font-family: '...';
        src: url('#') format('...');
        font-weight: ;
        font-style: ;
      }
    
Like mentioned previously, font-family:  can be used for generic font classes (serif, sans-serif, and monospace) and also for specific font family names.
Using @font-face, fonts can be named in relation to their files. This can be the same for the whole family (i.e. font-family: 'Playfair Display') or specific to different variations (i.e. font-family: 'Playfair Display Bold') depending on how the rule is structured.