Do you want Speed / Security or both?
Modem comes from the words (modulate / demodulate) or in other words it converts one type of signal into another type of signal. In the case of ADSL or VDSL the Draytek DV130 is our go to device to convert the Telco's signal into something that your computer can understand - Ethernet. We do not recommend the modem by itself we strongly recommend the installation of a robust firewall protecting your staff and your business.
A router is like a set of traffic lights moving traffic in the direction that it needs to go. For example you may have a computer accessing web mail while at the same time someone is talking on a sip phone. The data is routed from the modem through the router and out to multiple devices simultaneously.
Sophos - Cyber security made simple. Offering powerful unified threat management for your entire network, endpoint, mobile and web security along with a vast range of automated reporting helps you keep cyber threats at bay.