An anomaly is something that deviates from the standard, the norm, or the expected. And in the world of data, anomalies, despite our best efforts, happen. While there is often little you can do to prevent data anomalies, there is a great deal digital analysts can learn from them and Google Analytics provides a powerful opportunity to do that.
Google Analytics scans your data (be it website or mobile data) and provides those insights within the dashboard of each view. If there happen to be anomalies within any time-series data reports, hollow bubbles will appear, enabling you to hover over them to receive of a summary of the event.