The Grid is set of lines that help you position objects in your workspace with more precision. They are not objects and do not appear when publishing.
To display Grid Lines, select Object > Show Grid in the main menu.
You can set the Grid Frequency in the Preferences dialog box.
The Snap To Grid helps you align objects with the grid lines. When this feature is enabled, you can perform operations such as Move, Resize, Change Rotation center, Modify Shape, only snapping to grid lines so that the objects are aligned with the nearest grid line.
When in Snap To Grid mode, press ALT to not apply the feature to the current objects.