The Snap To Grid option lets objects align vertically and horizontally to the nearest grid marker. When you move an object with Snap to Grid ON, the handles of the object are forced to the nearest grid point.
Each object has a rectangular area associated with it. This rectangle defines the eight handles of the object: four marking the corners of the rectangle and four marking the midpoints of each side.
Snap to Grid is a toggle switch. The first time you select Snap to Grid, the snap is turned ON. The second time you select Snap to Grid, the snap is turned OFF.
How to control Snap to Grid