I did not wish to continue offtopic on Ni thread so I've posted here instead
According to original Jungian definition there's only one F but it can be flowing in two directions: either from inside to outside (extroversion) or from outside to inside (introversion). You can't go into two different directions at once. It's the same for N, S and T.
According to wiki: "This idea is interpreted in terms of whether the person finds it more rewarding when using the function in question to have an outward focus on people and things (extroversion) or an inward focus on thoughts and ideas (introversion). These models do not claim that people are only capable of applying the function in question in that attitude, but rather that operating in the opposite attitude requires the expenditure of "energy" (or rather, emotional resources, enthusiasm, and so on) whilst operating in the person's natural attitude replenishes that same energy."
As for practical uses I collect rewards from both Fi and Fe
But sharing emotions seems to work better.