The preceding media query example did not use a grid. You may be wondering what a grid is and why you should use it. Grid-based layouts divide your design into a collection of equal-sized columns and rows. Content and graphical elements can be organized according to this layout. Grids help in creating a logical and formal structure for designs. It prevents inconsistencies between the original design and the final implementation in HTML as designers and developers work with the same grid.
Grids are also helpful in responsive design, because the grid's columns can easily be rearranged to fit different screen widths.
In the preliminary chapters of this book you already read about CSS modules that defined layout structures. Flex boxes and columns can be used to define CSS layouts and grids. Although these layouts are responsive by default or can easily be defined as responsive, they are not the common way to define your CSS layouts yet. As mentioned earlier...