The World Imagery basemap is updated regularly with newer imagery. When and where updates occur, the previous imagery is replaced and is no longer visible. In the vast majority of cases the updated imagery is better, more recent, and is preferred, but there may be exceptions. For example, the previous imagery may better align with your GIS layers, or may offer fewer clouds or snow cover. Wayback will allow you to use the version of World Imagery that best suits your needs.
This first blog tutorial explains how to find a Wayback version you like to use as a basemap:
https://www.esri.com/arcgis-blog/products/arcgis-online/mapping/wayback-custom-basemap/
This second blog tutorial covers all of the tools in Wayback that you can use to explore Wayback imagery and compare change over time:
https://www.esri.com/arcgis-blog/products/arcgis-living-atlas/mapping/use-world-imagery-wayback/
