A Grid Lsyout looks like this:

QuotesIn is a good example of a Grid Lsyout. Note that the width of the screen determines how many grid boxes appear horizontally, and that when displayed on mobile, will most likely look like one box stacked upon another.

You can see in the preview on the right, it's limited to two columns due to the amount of screen width left, but the base theme shows four columns on the left hand side in the preview.

Screen width is a huge factor in design since the advent of mobile devices. Note that this layout also doesn't make allowances for sidebars, which are very useful parts for information design.

Because themes must adjust dynamically to accommodate various screen sizes for mobile devices, I don't particularly recommend a grid layout for your website. Still, as in everything else here at WA, it's your business and your decision.