I have seen a few wireless networks that have been set up where the SSID (Service Set Identifier) or your network name is hidden under the assumption that it will be more secure.
This means you take a device into the range of the router and the device will not see the router.
The article below will describe why this should not be done.
My main complaint with hiding the SSID is connection issues ( iPad in particular ).
More time should be spent making making sure your network with WPA2 and passwords that contain letters and numbers and not words out of a dictionary.