A simple non-printing, non-exporting grid can be displayed on your page to help you lay out layer content more accurately.
The gray grid is overlaid over your page to help you align objects. It is automatic, i.e. its frequency of grid subdivisions changes as you zoom in/zoom out.
Grids work best when combined with snapping, in particular when the Snap to Grid option is enabled. They are based on the currently set document unit.
At all zoom levels the grid shows as grid 'blocks' further split into grid subdivisions.