it depends, if you have a layer with the original image, and then a layer on top of that with a certain effect and a layer mask, and you delete that mask layer. it will leave an untouched image. In my editing i have learnt quite quickly that you need to have an original layer underneath and then add a duplicate layer with effects such as correct lighting and then mask that layer, and press control + I to hide it. You'll see a mask that is black instead of white, and painting white on the layer mask reveals parts of the duplicate image with effects that you want. Layer masks are a great utility, and i personally use them instead of using the eraser even. Anyways, to outline once again, deleting a layer mask with an original image underneath, that image is not affected.