A modem is a device that sends and receives data from your home and the Wide Area Network (WAN). This transmission of information allows your modem to turn your inbound fibre optic connection into an Ethernet and WiFi connection, which allows you to connect to the Internet.
Your FibreTel modem is a single device with an integrated router and modem (ont gateway). Together, they connect your home to the Internet and direct a signal to all of the devices in your home.