Mobile-first design means creating apps and websites that work best on your...

https://www.newpelican.com/articles/why-mobile-first-design-has-become-the-standard-for-modern-digital-services/

Mobile-first design means creating apps and websites that work best on your phone. It loads quickly, so you’re not waiting around. Buttons and menus are easy to tap with your fingers, and navigation is simple to find and use