A modem connects your computer to the Internet. It's a device that allows computers to communicate via telephone or cable lines.
A modem/router combo is a device that contains both a modem and router in one. With it, you can connect multiple WiFi-enabled devices (phone, tablet, laptop, etc.) to the Internet.
eMTA stands for "embedded multimedia terminal adapter." An eMTA modem combines the functionality of a modem and a phone adapter in one device. eMTAs are used by customers that subscribe to our Phone plan so that one device is able to provide both Internet and phone service.