A bed sham is basically just a false front pillow cover that is mainly used for decorative purposes.
Pillow shams are not really meant to be slept on but some people do however they can be uncomfortable to sleep on.
However some people also use the bed shams or pillow shams for support while they read or watch TV in bed and then remove them for sleeping.
The pillow sham basically is a false pillow that you cover your regular pillows with for styling and decorative purposes.
I have them on my bed as well and they do make great supports when sitting up in bed on my laptop or while reading a book or watching TV.
But the pillow shams are not very good to sleep on.