The grid layout is a two-dimensional layout system.
Grid examples
The following grids all have the same HTML.
<div class="grid">
<div>1</div>
<div>2</div>
<div>3</div>
</div>
But their layout is determined by CSS.
Simple grid layout
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grid-template-columns: 1fr 1fr 1fr;
Which can also be written:
grid-template-columns: repeat(3, 1fr);
fr
simply means a fraction of the whole. So this instruction reads, "repeat a single unit of fr three times".
Since the fractions are the same, 10fr or 100fr are both valid, and would have the same effect.
Unequal grid layout
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grid-template-columns: 10fr 1fr 1fr;
This instruction reads, "make the first box 10 units long and the next two 1 each ".
Responsive grid layout
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grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
Which means, "fit in as many boxes on a row as possible, so long as they are at least 200px wide ". Use the Chrome DevTools to narrow the width of the screen until you see a change in the layout of the three boxes.