Backpack is a feature in Plants vs. Zombies: All Stars where all the player's collected consumables and Puzzle Pieces of plants, weapons or armor are stored. It is unlocked automatically when Plants vs. Zombies: All Stars is played for the first time. There are three different sections of the feature.
The location of items is written in the "information" button, which will mention what level the item can be found and the rarity of it. Some items do not have their own level where they can be found.
All items in it can be sold for coins, though the higher the rarity of an item, the higher its payout will be.
The player's kept puzzle pieces of plants are stored here. They will be automatically added when the player gets a new plant puzzle piece from various methods. The amount of puzzle pieces the player currently has is recorded with a number, and if the player has 30 puzzle pieces for a plant, it is ready to be formed to an actual plant.
Armor and weapons, including their puzzle pieces, are stored here. Every used item is marked with "equipped". When in this state, they cannot be sold unless the item is taken off. The player can have duplicates of an item. Level 2 and 3 equipment can be formed with 10 and 40 puzzle pieces of itself respectively.
Items other than puzzle pieces are stored here. Most items in this compartment are usually not able to be found in usual levels, but are often in daily rewards, limited-time levels or events.