Team News is one of the great features, among many others, that is part of Modern Team sites. This feature consists of an out-of-the-box WebPart placed in the site home page that allows to add new News to the Team Site and display a list with the last news published in the site:
Both functionalities (creating News and see a list with the site news) are provided by this WebPart built with the SharePoint Framework as you can verify editing the site home page:
If you press the “Add news” button, the page creation process is automatically started so you can add static content or dynamic one (by means of SPFx WebParts) to the new page created:
When the page is ready, just publish it so you can verify it is shown in the home page as the most recent news published:
Finally, if you ask yourselves where are stored the pages, you can check they are published in the Site Pages library on the site.