Most modern computers and laptops will have a built-in modem. Nowadays modems don’t exist as a physical, separate box – as you would find with a router.
Modems translate the information sent to it through your router so you can watch videos, check emails and use Facebook on your computer.
Computer information is stored digitally but the information sent over your phone or cable lines are analog waves.
Think of the modem as a translator it takes those analog waves and converts them to digital signals and then delivers them to your computer.