I'm trying to learn how to change a background from a green screen. I have watched multiple youtube videos on it and I get through most of the steps but then it says to select 'inverse' and press the backspace button and my photo goes all one colour instead of having a white background. Please help!
People deleting Layer content instead of using Layer Masks often seems to be a sign that they do not care terribly much about best practices.
If the whole image fills at deleting it could be that you are working on the Background Layer and do not have an active Selection or the Selection covers the whole image.
But you have not really given the pertinent information about what you have done, what the Selection is, what the Layer structure of the file is etc. so please post screenshots to clarify of this Forum directly.