Captive portal
From Free Knowledge Base- The DUCK Project: information for everyone
A captive portal describes the webpage that asks for authentication, payment, and/or acceptance of terms of the agreement in order to access the Internet via a public provided WiFi hotspot you might find at coffee shops, airports, business centers, or hotel lobbies. You may simply be asked to accept their terms or you might be prompted for payment.
The use of Captive Portals relates to WiFi aka Wireless Internet primarily and at publicly provided hotspots.