What is the work$-$energy theorem?

I think, therefore I am$.$

$K.E_{.\text{i}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l}}+P.E_{.\text{i}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l}}+W_{\text{n}\text{o}\text{n}-\text{c}\text{o}\text{n}\text{s}\text{e}\text{r}\text{v}\text{a}\text{t}\text{i}\text{v}\text{e}}=K.E_{.\text{f}\text{i}\text{n}\text{a}\text{l}}+P.E_{.\text{f}\text{i}\text{n}\text{a}\text{l}}$

vec$(F{)}_{1on2}=-$vec$(F{)}_{2on1}$

$W_{\text{n}\text{e}\text{t}}=K.E.$