Minecraft wiki entry for Item_(entity), associated text: Entity data
Tags common to all entities[show]
 Age: The number of ticks the item has been "untouched". After 6000 ticks (5 minutes) the item is destroyed. If set to -32768, the Age does not increase, preventing the item from despawning automatically.
 Health: The health of the item, which starts at 5. Items take damage from fire, lava, falling anvils,‌[Java Edition only] and explosions. The item is destroyed when its health reaches 0.
 Item: The inventory item, without the Slot tag.
Tags common to all items[show]
 Owner: If present, only the player with this UUID can pick up the item. Used by the give command (and can be set in a summon command) to prevent the wrong player from picking up the spawned item entity.
 PickupDelay: The number of ticks the item cannot be picked up. Decreases by 1 per tick. If set to 32767, the PickupDelay does not decrease, preventing the item from being picked up.
 Thrower: The UUID of the player who dropped the item. Not present if the item was not dropped by a player.