1. Reassortment is the rearrangement of genes from two distinct influenza strains to produce a novel viral strain.
2. The genetic material (RNA) of the influenza virus is in eight separate segments. If a cell is co-infected by two viruses of different genetic make-up (either different strains or different sub-types), the eight segments can "mix and match" so that a virus with a new combination of the eight segments is produced. In theory, two viruses, each with eight segments, can produce 256 different combinations.
(2008, Geary W.Skick. Protecting your business in a pandemic : plans, tools, and advice for maintaining business continuity. ISBN: 978-0-313-34602-6)