Why not get a very good book on it.Try looking in your local library first (and if they are on t'internet then you may be able to search the catalogue all over the county).You might have to resort to an earlier version of Elements but it should get you started and provide info on Layers.
Then you might find a new or second hand one (I'd look in Amazon).
Also there are copies of adobe Photoshop booklets around as magazines in good newsagents.They will make layers very clear as Elements is a stripped down version of Photoshop(any old Photoshop book should be helpful),
I would try and explain BUT I'm entirely self taught and my way to teach it is to show by example.
The best way to regard layers as being like a sandwich.You can insert images,layer two or three different photos together to get a combined image,use a filter on one image and insert it into another,use mask layers,use another layer to add text..
The use of layers is endless.
The
Adobe Free Exchange is a good resource