The HP un2420 Mobile Broadband Module Ethernet Adapter is a device used in some HP laptops (and possibly other devices) to provide mobile broadband (WWAN) connectivity. It allows your laptop to connect to mobile networks (such as 3G or 4G LTE) via a SIM card, functioning as a mobile hotspot or data connection adapter. The "Ethernet Adapter" part in the name indicates that it appears as a network adapter in Windows, which is responsible for handling the internet connection via mobile broadband.