Hi ;)
Question n.1:
"Default routes are used to direct packets addressed to networks not explicitly listed in the routing table. Default routes are invaluable in topologies where learning all the more specific networks is not desirable, as in case of stub networks, or not feasible due to limited system resources such as memory and processing power."
Default route = gateway of last resort
See that:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml
Question n.2:
"A discontiguous network comprises a major net that separates another major net."
See that:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093fd6.shtml
HTH
Andrea