What does this Zurb Foundation 6 mixin mean
@include xy-grid();
Which one does it define, grid-x or grid-y?
@include xy-grid;
This only does display: flex.
You can also use the mixin with arguments to make it vertical (grid-y):
@include xy-grid($direction: vertical, $wrap: false);
API docs: https://foundation.zurb.com/sites/docs/xy-grid.html#xy-grid