These are coordinates that have been changed by the user, normally for a Mystery, Wherigo or Multi cache to indicate the final location.
Corrected Coordinates are synced both ways with geocaching.com. You can create them in Cachly or on the geocaching.com website.
The icon for caches with corrected coordinates will show on the map at the corrected coordinates and not the published coordinates.
If there are Corrected Coordinates then the cache icon displayed on the map with have a red triangle added.