What is it
Back in June 20, Google advised that it was about to launch new promoted pins for GMB Local ads in Google Maps.
But only now they appear to be live:

How to
If you wish to participate on the promoted pins, you will need to use a Google Ads account.
Conclusion on this Google My Business Update
To be honest, I don’t know if you will attract more customers with promoted pins as they can pass unnoticed very easily by customers. You can always test it with a small budget.
Be Remarkable!
References:
https://www.seroundtable.com/google-maps-square-pins-for-ads-30314.html
https://twitter.com/ndyjsimpson/status/1319274594222551042
https://www.blog.google/products/ads/helping-businesses-and-nonprofits-recover/