The Snap to Objects option in Flash affects several tools, but most primarily the Arrow Tool. When you have Snap to Objects selected under the Arrow Tool's options, it affects how objects that you drag around the stage move in relation to each other. Objects that you're moving are more likely to "snap", or jump, to the edge of the nearest object, moving along the vertex points delineating the object's shape. Turning this option off lets you drag your shapes more freely.