You're happily tinkering away on the internet until something happens and your laptop's like, "Surprise! You're no longer online! " And you're like, "Ah! Something must be wrong with the modem or the router or something! "
But in order for that sweet WiFi to flow unobstructed into and throughout your home, both the modem and the router must be working. Sometimes they can be combined into one box, but even so, it's still two different technologies working inside of a single housing. Here's the difference between them: