Quest Collection Items are a designation of quest items that are specifically collected for a given quest. These items are typically common rarity. The items' tooltip displays the quest it is related to under the item name. Most quest collection items are collected as drops from specific NPCs or from interactive objects. These items are not always 100% drop rate and will drop regardless of character level provided you have the quest.
For a list of all documented quest collection items sorted by their rarity, see Category:Quest collection items.