What Is A Default Route/Default Gateway?

Have you ever wondered what the purpose for the default route was?  Most networkers know already, since they deal with this almost every day.  But for those of you new to networking, the default route is set for any packet from a device destined for a a network other than the network the devices lives on.  Thats a little confusing, so let me put it this way.  If your PC, or whatever, lives on 192.168.10.0 network, with a /24 subnet mask, then any destination that is not 192.168.10.0 - 192.168.10.255 will be sent to the default gateway (default route) address.  This means that packet has to be routed to your default gateway address.  So if your PC has an IP address of 192.168.10.5 and your default gateway is 192.168.10.1, and you are trying to send to an IP address of 10.10.10.2, then the packet has to go to 192.168.10.1 first, then to 10.10.10.2.
All devices has to have a default route (or a default gateway) if they want to talk to other devices on other networks.  (That is not completely true.  You can have static routes, but that is another topic.)  I hope this clears up the what a default route is.  And to note, the default route and a default gateway really the same thing, so dont let terminology trip you up.

Addition to this post because of a conversation that took place:
Ok, one of my coworkers has called me up and tried to 'school me' on the difference between a default gateway and a default route.  Yes, there may be a difference in that one applies for 'the client' (default gateway) and the other 'for the routing table' (default route).  However, they perform the same function AND if you look on your PC, the 'default gateway' IS part of the routing table.  Go into CMD and do a 'route print' and you will see the routing table (and the 'default gateway' is actually the 'default route' in the output).  Some people say that the default gateway is for 'devices' like a PC or a switch.  That is true, but remember, you can use a PC as a router (L3 device).  So as my buddy would say, there is a .0000001% difference.  To be fair, if you configure a 'default gateway' on a switch, that does not show up in the routing table.  It is for the switch only and you still have to have a default route configured to route traffic (on a L3 switch).  I get what my buddy is saying.  So, with that said, there is truth to it that there is a .0000001% difference.  But, it also depends on the device.  For a switch, yes, there is a difference.  But for a PC, no difference at all.