Rebooting, or Powercycling, means powering off and turning back on the equipment. This usually fixes most broadband connection problems, as sometimes the modem thinks it is still connected because of its 'memory' from the previous connection.

When you powercycle the router/modem, the device disregards the corrupted connection and then requests a new connection ID from the DSLAM (Digital Subscriber Line Access Multiplexer) at the phone exchange. This is not a problem with your broadband modem, it is common thing that happens to the DSLAM network hardware for broadband users.

So next time you cannot get a connection, remember to powercycle your router/modem.