When you open iTunes, it checks whether you have iTunes Store purchases that haven’t been downloaded to your computer.
You can also check anytime. You might want to if, for example, a download was interrupted.
To make sure all your purchases have been downloaded:
Make sure you’re connected to the Internet.
In iTunes, choose StoreÂ > Check for Available Downloads.
Enter your iTunes Store account ID and password, and then click Check.
Purchases not yet on your computer will be downloaded.
The Purchased playlist displays all your purchases. However, because you can add or remove items in this list, it might not be accurate. To see all your purchases, click iTunes Store, click Account, log in, and then click Purchase History.
If you delete the Purchased playlist, iTunes creates a new one when you buy an item from the iTunes Store.