An Azure service that integrates speech processing into apps and services.
Well when you sign up for the free Azure account, you'll get a credit (think it was $200) and a year to try everything out. After the time or the credit runs out, it'll stop working as you say. Technically it'll do more than just stop working - your account actually gets decomm'ed/frozen and you won't be able to log back in until you sign up to start paying in some fashion.
Oh and after 30 days or so, MSFT will start to nag/bug you to sign up for at least the 'pay as you go' tier. If you agree to or accidentally switch over - you'll get to continue on with the free tier up to the year and then they'll start billing you at 'pay as you go' rates.
If you don't agree, MSFT (even though they have your credit card) will not bill you automatically so if you have some special set up or code, make sure you do what you need to map out, document, export whatever you've created before or you'll be locked out and have to pay to get it out.