When you make adjustments to an image using Lightroom you are looking at the original image and using it as the source for making the adjustments. But all of those adjustments are being stored in the catalog which is a database. None of those adjustments are being applied to the image file itself. The image is left in its original state. If you then delete that image from Lightroom and choose the option to delete from disk, you completely discard the image as well as all of the adjustments that you have made to the image. If you choose to delete the image and the option to remove from the catalog, the image will be removed from Lightroom, but will remain in the folder and all your adjustments will be discarded. In either case, you want to take care in deciding what happens to the image file. If you want to keep it then deleting is not a good choice.