Answer Description
When a wireless network broadcasts it includes the network name, called a Service Set Identifier (SSID). Most commonly the SSID will be a user-friendly name to help people identify which network they want to connect to (e.g. Smith WiFi, Friendly's Guest, etc.). Disabling SSID broadcast will still allow the network to be visible to nearby devices but in order to connect to the network they will need to know the SSID (as well as a password/key if configured).