SSID (Service Set Identification)
From DD-WRT Wiki
Service Set Identification
You can choose to broadcast it on an AP or not. A client needs to know this ID to asociate with an AP.
On the current implementation of DD-WRT (23sp1) special caracters that seem to work with windows are not supported and refuse to be configured and fail to connect. Example: Unsupported Characters in SSID "¡Bienvenidos! AMPM"