What is difference between UTP and F/UTP?

UTP: Unshielded Twisted Pair

Four pairs of two insulated copper wires twisted around each other to reduce crosstalk or electromagnetic induction between the pairs. No metallic foil or braid is present.

F/UTP: Foil Over Unshielded Twisted Pair

Four pairs of two insulated copper wires twisted around each other to reduce crosstalk or electromagnetic induction between the pairs with an overall metallic foil wrapped around the pairs