Mobile-first design means building a website or app starting with phones in...

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

Mobile-first design means building a website or app starting with phones in mind. It makes pages load faster, so you don’t get stuck waiting. Buttons and links are big and easy to tap, perfect for your thumbs