Product specifications describe the exact model in the listing. A blade's full length can be longer than its cutting edge. Compare like-for-like measurements when looking at two saws.
PPI means points per inch. Fanno models list different PPI values and tooth patterns, including lance, tri-edge and raker designs. These fields help distinguish the models; they should be read together with the intended use and the product instructions.
Also check handle details, blade origin and included items. Some listings are complete hand saws, while others are replacement blades only. Read the description and specification table together, and ask the store if any detail affecting your choice is unclear.