Im trying to get all the formulas for work correct, heres what i have so far:

W = Fnet * d * cos & (& is theta)

W(gravity) = none , because & = 90 degrees

W(Normal force) = none , again because & = 90 degress

W(friction) = - F(friction) * d (- because & is 180 degrees)

Work energy theorem = delta KE = 1/2 mVf^2 - 1/2 mVi^2

when exactly do we use the Work energy theorem???

W(spring) = 1/2 k(Xf^2 - Xi^2)

Im confused over W(gravity) being none because I also thought that W(gravity) is mgh which is potential energy, can someone clarify work or gravity and potential energy for me and explain WET as well, i know this is a lot of questions in one, but its very confusing to me. Thanks!