If you have a Nexus or Pixel device running Oreo, you’ve likely seen the “[app name] is running in the background” notification. If you have a Pixel 2, you may have seen this notification, though the verbiage is slightly different—it reads “[app name] is using battery.” While useful, this can also be quite annoying. Fortunately, you can pretty easily turn it off.
Source: How-To Geek