The grid and its lines allow you to place items in the drawing by aligning them with the grid lines or nearest intersection of the grid lines. You can use the grid if you want the items to line up at regular intervals in the drawing.
The grid is a set of imaginary lines in the drawing; they do not appear when you print the drawing. When you select View > Snap grid, items always align with the grid lines or nearest intersection of the grid lines. You can view the grid by selecting View > Show grid.
You can change the display of the grid from static to dynamic by setting options on the Grid tab of the View Properties dialog. To view grid lines at a finer level, set the style to dynamic and adjust the density.
The grid lines for a dynamic grid move as you zoom in or out in a view. You can set dynamic grid lines to appear at fine, medium, or coarse levels. The grid lines appear at common major measurement increments. A dynamic grid displays index lines that intersect with the darker, solid grid lines.
A static grid displays solid grid lines that do not move as you zoom in or out. You can specify the increment settings on the Grid tab of the View Properties dialog.
You do not have to display the grid in order to snap items to it.