Holy grail layout solution that makes complex apps being usable on mobile?

1. Why is it called holy grail layout?

Why is it called holy grail layout?

The main body of content occupies the center area, with two panels of supporting content or interface elements on either side. The name "holy grail" refers to a legendary sought-after thing. In the early 2000s, it was difficult to reliably achieve the holy grail layout using existing web technologies.