There are two types of Gear: special cards used by PCs, and keywords most commonly found in Adversary entries.
Gear cards used by PCs represent weapons, armor, tools, expertise, and more. They consist of a piece of equipment used for some particular purpose, or in the case of expertise, a set of related equipment, training, guild memberships, and the like for a particular skillset.
Gear must be equipped to be used. Once equipped, Gear provides any listed bonuses or effects and grants access to any entries on its card, such as Actions and Reactions. In this manner, Gear provides a set of basic abilities that a PC can always access regardless of what cards they have in their deck and hold in their hand.
In order to equip a Gear card, you must have available a slot in which to equip it. If there are no available slots, you must first unequip another Gear card. See the Player's Guide for more information on slots.
In combat and exploration scenarios, Gear can be dropped in the occupied section or region. Doing so is free (does not require the Strategy Phase), even if it is equipped; this would immediately unequip the Gear. Similarly, Gear can be freely handed to an ally in the same occupied location, even if equipped. These activities do not permit equipping any new Gear in the freed slot, and they do not bypass the restrictions on unequipping clothing and armor.
Most Gear can be used repeatedly. However, Items are unique in that they can only be used once per scenario. Specific Gear entries may provide other limitations for their use.
Some Gear cards have a level requirement. A PC must be at the required level or higher in order to equip the Gear.
All Gear cards have a Wealth entry. This is the cost in Wealth that a PC must pay in order to purchase the Gear. Likewise, a PC gains this amount of Wealth if they sell the Gear. Economic conditions, story considerations, and other factors may alter the actual Wealth value listed on the card; the DM determines the actual Wealth paid or gained when buying or selling.
For Adversaries, the Gear keyword denotes an entry as being reliant on physical Gear. Some PC abilities can force an enemy to drop or otherwise unequip Gear, which would then make the corresponding entry or entries unusable. In other cases, Gear might represent throwing weapons or the like of which the Adversary has a limited supply; once the supply is exhausted, the Adversary cannot play the entry without picking up a previously-thrown Gear.
For more information, see Player's Guide Chapter 7: Gear and Wealth.