Hi,
There are products that are "always-free" and there are products that are "free for 12 months" during the Azure free account period.
You'll find more information here:
https://azure.microsoft.com/en-us/free/
Click on the "View Full list of products free for 12 months" and "View full list of always-free products" for more information.
Here's also some more information:
https://azure.microsoft.com/en-us/free/free-account-faq/
Best regards,
Leon