Hi celine2609
After adding the Creditcard you have a credit of $200 each month by Google. If you have a lot of visitors on the pages where the map is loaded, then it is possible that your cc will be charged.
If you decide to not add the cc, your map will not be working properly.
See: https://developers.google.com/maps/documentation/javascript/usage-and-billing
Hi clariealberts
As you suspected, it is due to the new terms of use of the Google Maps API.
These have been revised recently.
You need to link a creditcard and eventually enable some packages of the Maps API in the Google Cloud Console.
Hope that helps.