@Egg

in photoshop there is only the image, there is no page background

the default layer of a new document is called 'background' and cannot have transparency - but once you have added a new layer which is transparent by default you can delete the 'background layer if you wish - similarly if you open a single layer image and you want to work on it with transparency you need to right click and select 'make layer from background' which effectively copies all to a new layer and deletes the original