You just opened a project in ArcGIS Pro and a little message popped up, warning you that a datum transformation cannot be found and that the data may draw with an offset.
If that sounds scary or confusing, read this article on ArcGIS Blog to find out why you are seeing it and what you can do: https://www.esri.com/arcgis-blog/products/arcgis-pro/mapping/transformation-warning/