It is along these axes that items can be aligned and justified using the properties defined in the Box Alignment specification .

In CSS the block or column axis is the axis used when laying out blocks of text. If you have two paragraphs and are working in a right to left, top to bottom language they lay out one below the other, on the block axis.

The inline or row axis runs across the Block Axis and is the direction along which regular text flows. These are our rows in CSS Grid Layout.

The physical direction of these axes can change according to the writing mode of the document.