about off-page:
Off-page connectors provide connection between schematic pages within the same schematic folder. An off-page connector is connected by name to other off-page connectors within the same schematic folder. Like-named off-page connectors in different schematic folders are not connected.
about port:
you can list the hierarchical ports of the selected schematic pages in the browse window and use this command to follow ports through a hierarchy when tracing problems in a hierarchical design.