Gear items are the most complex items Shadowrun has to offer. In addition to normal data items, gear items add two more concepts:
Variants: Some items exist in different versions (e.g. “Bone Lacing” has Plastic, Aluminium or Titanium variants, Low-Light vision exists as an optical accessory, as a cybereye implant (costing capacity) or a cyberware version (costing essence).
Alternate Usages: Some items have a secondary usage, e.g. the Ballistic shield is usually used as Armor, but can also be used as an exotic weapon. Armor would be the sort category under which the Shield is listed, but due to a secondary usage, it it can appear as a weapon too - with a totally different set of stats.
In a generic, not necessarily Shadowrun related fashion, gear and those concepts are described /wiki/spaces/RPGFW/pages/1250787330.