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 with some devices.
More time should be spent making making sure your network is secure with WPA2 encryption and passwords that contain letters and numbers and not words out of a dictionary.