Hello,
The Google Cloud Platform free offering has two parts:
A 12 month, $300 credit free trial
Free usage limits on selected products and features
If you sign up for Google Cloud Platform account for the first time, you will get $300 credit (not cash) for 12 months which will be applied to your billing account against charges you receive when using our products beyond their free usage limits . To see who is eligible click here.
In case you were referring to the Google Maps Platform, it has a monthly $200 credit free tier. See the FAQs for more details.