Hi Yvonne, and a big welcome from me, as well.
OP: "...My question is, if I import my photos from iPhoto to Photoshop, does it actually move them or does it just make a copy and leave the originals behind in iPhoto?..."
I'm 99% sure that Elements works just like it's big brother, Adobe Lightroom, with respect to the storage location(s) for photos: Importing a photo into LR (or Elements) does not move the originals. It merely generates a new entry in its image database that points to the image's current location. It doesn't copy, and it doesn't move the original image files. I have well over 200,000 images cataloged in LR (and in a couple of other image database systems), and I would never use any other system.
I'm not a Mac person at all, and never have used iPhoto even once in my life, but prompted by your question, I looked up how iPhoto stores photos. From what I read, in contrast to how LR/Elements work, when iPhoto imports a photo, it makes a copy of the image (not just a pointer to it) in a dedicated folder called an iPhoto "Package". This approach has some benefits, especially for small collections and inexperienced users, but, for many reasons, I would never want to be bound to such a rigid system.
Unfortunately, I don't know anything about the internal structure of an iPhoto Package folder. For example, I don't know if iPhoto might do something weird like attempt to compress all your images into groups, so I don't know if Elements Organizer will have any problem reading the contents of this / these packages since it is expecting to import ordinary image files (eg, JPGs, PNGs, TIFFs, NEFs, CR2s, etc.). Obviously, with the imminent demise of iPhoto, I suspect a lot of people have been migrating to Elements, so there is probably a lot of discussion on the internet on this exact concern. It should also be very easy for you to use Finder and look inside the package folder and make sure you see files of the types mentioned above.
HTH,
Tom M