By providing a PPPoE bridge, the connected device (firewall, router or PC) can log into the Internet (your ISP) directly and have full control over the Internet connection - that makes the Vigor 130 a unique product. You can connect any device to the Vigor 130 which has a PPPoE client facility, which includes PCs, most Ethernet-WAN routers and the Apple Airport/Time Capsule™ products.
Other Ethernet 'modems' may use workarounds to get a public IP address 'through' to your secondary device/client, requiring non-standard operation and complicated dual-stage setup (modem logs in, router routes) but the Vigor 130 provides the secondary device with a real routed IP connection and the ability to fully manage the connection, making setup easy. In most cases, the Vigor 130 needs no setup or configuration - just plug it in and set up your PC or router. All login/ISP details are entered on the connected client device, not the Vigor 130. The actual connection to your ISP is still PPPoA or PPPoE (depending on your ISP and line type).
This transparent bridging method also differs from using a normal ADSL/VDSL router which logs in itself and then uses NAT or multiple public IP addresses to create an onward client connection for your secondary device; that is not IP Address thrifty and can introduce secondary NAT compromises or interference with various protocols/traffic. With the Vigor 130 bridge/modem, you get a true single public IP address (or multiple, if you have them) straight through to your firewall/router.