Using sections, you can create beautiful and complex layouts. They can contain any kind of block and even other sections.
First column, one row.
Second column, first row ...
... and a second row.
Third column, first row ...
... a second ...
... and a third row.
You are in full control over flex properties such as the minimum block width, the gap size and the alignment of items.
Cards are basically not more than styled sections. They are a bunch of blocks combined in one section that maybe has a border, a shadow, padding and even rounded corners.