Custom fonts settings allow to upload font you like  but didn’t find in the Typography settings. All the fonts uploaded here will appear in the Typography settings having the same name you use here.

NOTE! Each additional font you use, will increase a bit the loading time for your site. We advise you to use as few different fonts as possible.

Each font added here can be used from ‘Typography’ settings.

Also you can watch a video tutorial how this option is used (the video is based on another theme, but the process is the same):