Google allows you to utilize Google Maps to add a map feature to the app you develop. To have access to the Google Maps data, you need an API key. You can get the API key of Google Maps from Google API Console, for free. But, there is a crucial thing you need to know first.
Since July 2018, Google applied a new policy to Google Maps usage. Every developer who wants to use the Google Maps platform needs to provide the credit card/debit to the billing info. If you don’t provide your credit card/debit card, you will see an error message like “for development purpose only” when trying to add a location. Does that mean you can’t use Google Maps for free?
Every month, you get $200 credit from Google to use Google Maps. This means you won’t be charged unless the use of Google Maps (via your API) exceeds $200 every month. The products you can use with the $200 credit given by Google include core Maps, Routes, and Places. You can visit this page to learn about Google Maps pricing.
How to get a Google Maps API key
To get a Google Maps API key, first, go to the Google API Console and login with your Google account. Before being able to create an API key, you need to have at least a project. To create a new project, click the dropdown menu on the top side and click NEW PROJECT on the top-right corner of the appearing popup.

Once you have a project, select it (via the dropdown menu) and click Library on the left panel.

On the top side, you will see several Google Maps APIs on the Maps section. Select ones according to your need and click ENABLE to enable the API.

You can enable the APIs based on the map type you want to use. You can read the brief description of each API before enabling it. For instance, if you want to add a map to your website, you can enable the Maps JavaScript API.

Once done enabling the APIs you need, back to your project main dashboard and click Credentials on the left panel. Create a new API key by clicking the Create credentials button and select API key.

A popup will appear afterward, providing you the API key. You can now use the API key on your app.

If you want to learn more, you might want to read how to use the Google Maps API in Java or React.