U/UTP or UTP is an acronym for Unshielded Twisted Pair. This means there is no shielding within the cable construction.
F/UTP or FTP is an acronym for Foil Twisted Pair. This means there is a foil shield that surrounds all four pairs.
U/FTP is an acronym for Unshielded / Foil Twisted Pair. This means there is no shielding that surrounds all four pairs; however, each pair has its own foil shield.
F/FTP is an acronym for Foil / Foil Twisted Pair. This means there is a foil shielding that surrounds all four pairs, as well as each pair having its own foil shield.
S/FTP is an acronym for Shielded / Foil Twisted Pair. This is the same construction as F/FTP, however the outer shield that surrounds all four pairs is made using a wire braid as opposed to a foil. Each pair having its own foil shield.