What are google maps terms of use?

Question

Google Maps

Good afternoon.
I read that since API version 3 google no longer requires a key for maps.
But the key is present in the Google instructions.
A card without a key works, but:
1. What threatens the owner of the site with the use of a card without a key.
2. How to view card usage statistics without a key.
3. Can I insert a screenshot of the map as a picture on the site, or do I need to change it somehow. If you need to edit, then as well as possible there are examples.
Thank you in advance if you poke your nose into something relevant on cards from 15-16 years old.