A CD is a physical disk and not downloaded to a computer. A CD is placed in the CD/DVD drive of the computer and installed from the CD.
A software Download is received using the internet from the TurboTax website directly to and installed on your computer.
If you downloaded the TurboTax software on computer A, then you can download the same software to computer B from the TurboTax website.
You will need to access your TurboTax download account by signing onto the website with the User ID you used to purchase the download software - https://shopping.turbotax.intuit.com/unified/downloads?route=myaccounts&cgcview=downloads
