Mobile-first design means creating apps or websites that work great 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 or websites that work great on your phone first. It’s built for speed, so pages load quickly, and uses big, easy-to-tap buttons for smooth thumbs-only use