Right-angle weave stitch
In right-angle weave the thread passes through each bead at a right angle to the last, so neighbouring beads lie across and along in turn. The chart alternates them the same way, and a unit of four reads as the square it makes.
A RAW design drawn on a straight grid looks half a bead off everywhere, because it is. The alternating lattice puts each bead where the thread leaves it, so a design reads as the squares it makes rather than as a grid. Counts are by bead, not by unit, which is what you buy.
Word chart
Reads left to right, one row per line, in the order the beads are picked up across a row of units.