Who doesn’t like free stuff? The public cloud vendors know we all do.
The major cloud services offer their wares to everyone from the indie developer with a credit card to enterprises that cut seven-figure SLAs. The big three—Amazon AWS, Google Cloud Platform, and Microsoft Azure—also offer free trial versions of various individual services unde their banners. The free offerings are not always enough for full production work, but enough to get a good taste of how the services work without running up a bill.
Note that the list of always-free services varies widely between clouds.