In English this can also be a "pillow slip", but maybe this is very old-fashioned and I am showing my age!
It's probably regional but I'm not sure. I'm Australian in my 50s and always used "pillowcase" but I've heard "pillowslip" many times. It just feels either more old fashioned or more British or more posh to me.
The face of the sheet?
Great isnt it. Very logical in Romanian.