The Backpack.
Your books.
The Backpack is an item that you have throughout all of the original MySims. Inside the backpack, there are five different sections.
Essence Book[]
This book lists all of the essences you have discovered under their associated interest. It also tells you how many of each you have which may aid you when trying to complete tasks.
Task Book[]
This lists all your current tasks you have. It gives you information on each, including: the status of the task; the essences required; introduction to the task dialogue; and what you are actually required to make.
Backpack Storage[]
Here will be all of the objects you have built in your workshop, or collected from Sims' houses, that haven't been placed anywhere else.
Blueprint Book[]
A list of all the various blueprints you've unlocked will appear here through both improving the Star Level of your town and completing tasks.
Relationship Book[]
This book will have records of all Sims you have interacted with, giving you a brief profile for them as well as telling you their interests. It will also tell you what your relationship status is, whether you are their Acquaintance, Friend, or Best Friend.