If we want to access the internet in our home or business, we should have a modem. The main reason we have to use a modem is because there are two types of signals that are used when we connect our computer to the internet. Our computer can only understand digital signals, while the phone lines which help to connect the internet are works on analog signals. A computer cannot communicate directly with your ISP phone lines, both the computer and the internet are works on different signal types that's why we use a modem, which is used as a signal translator between your computer and the internet.