How do recommendation letters work?

I’m thinking about applying regular decision to Georgetown. How do the recommendation letters work? How many do I send in? How do teachers submit their rec letters (is it through Naviance, or do I need to make an account for Georgetown Applicant first)?

Do teachers send in electronic copies or do they have to send them in by mail?

Seek, and ye shall find: https://uadmissions.georgetown.edu/first-year/application/teacher-report