The TurboTax download version and online version are two separate versions of the software. If you are using online, you are in a web browser and went to www.turbotax.com and created an account online to prepare your return. The download is actually installed on your computer and you open it to prepare the return there on the computer.
If you are using the Online version, you will have to do a new, separate online account (with a different user ID) for each federal return you want to prepare and purchase for each (if you need to use a paid version of the online software). If you do another return under the same username you did your own return, it will override the one you already filed and lose everything for that return. It's always been this way online.
When you click on Buy Now, it will ask you to select download for either PC/Windows or a Mac. Or you can choose to select the link right under those that says "I'd like to order a CD" if you prefer to have a CD shipped to you.
The CD/Download (desktop version) product is a better overall value for people who prepare tax returns for their friends and family. This one will allow you to prepare and print unlimited federal returns and e-file up to five at no extra cost. You can find the desktop versions here https://turbotax.intuit.com/personal-taxes/cd-download/
