Google apparently thinks you don't have enough ways to search Google on your phone. On my Pixel, I have the Google search 'pill' on the home screen, and Google Assistant if I hold down on the home button or use 'OK Google.' If you have Chrome Dev, you can use a new search widget as well.
All joking aside, I can see this being useful for some people. Tapping on the widget instantly opens Chrome with the address bar highlighted, so while you can use it for basic searches, you can also use it to open websites without tapping on Chrome first. And since it uses Chrome's address bar search, it will use whatever search engine you have selected in Chrome.
The widget was developed as part of an anti-trust lawsuit settlement in Russia, where Yandex claimed Google had violated local competition rules. The terms of the agreement required Google to offer a search widget that could change search engines, which will replace the standard Google search widget for Russian devices.
You can try this for yourself by downloading Chrome Dev (or Canary), then dragging the new 4x1 widget to the home screen. I don't think I'll ever use it, but it's there if you want it.