All the items and resources that you collect, produce or otherwise obtain in the game are stored in your inventory.
You can access the inventory by tapping on the backpack icon in the lower-right corner of the screen:
 
 
There, you can check how many items and resources of different types you have and how to obtain them:
 


The number under each item indicates the total amount currently available on your game profile. Tap on an item to find out how it can be acquired or used:
 
 
Can I sell items and resources stored in the inventory?
There is an option to sell certain items and resources for coins directly from the inventory. Typically, the items that can be sold are produced on the farm, like plants and animal products.
To sell an item, tap on its icon in the inventory and select the amount that you would like to sell:
 
 
The inventory has an unlimited capacity, so you can store as many items as you like there.