Routers are computers, but since they don’t have keyboards and monitors attached, they must be configured in alternative ways. Typically, this means that the vendor has built a tiny web server into the router, and then you can simply use a browser to interact with the router to configure it.
These configuration screens are password protected, since they contain sensitive information that would otherwise allow outsiders full reign of your home network. They’re usually only available to computers that are inside the home – hackers cannot get to them and try to guess your password because they can’t get access to them.
But what do people do who aren’t computer-savvy enough to understand how to configure their routers do it? Well generally, they get a family member or friend to help them out. When this person gets tired of driving across town to get access to the router, they’ll sometimes enable Remote Administration on the router. This will make the router’s configuration screens available to anyone on the internet. The idea is that doing this will make the life of the tech-support helper much easier, but it also makes that network much easier to attack.