OSPF areas

Hi,
        Can an OSPF router be included in two OSPF areas? What is the
definition of an OSPF Area Border Router, is it - A router that is part of a
single OSPF area (the router has only one link state database) but has an
interface that connects to a different area? OR is it - a router that is
included in two different areas (the router will have two link state
databases)? Does Area Border Routers have copies of the link state databases
of all areas it connects to?

rgds,

Joseph Placid