Intuition behind Evidence function

Question

I understand the formal definition of Evidence function. If we define an experiment $E= \{X,\theta, f(x\mid\theta)\},$ where $X$ is a random vector with pmf $f(x\mid\theta)$ with parameter $\theta,$ then for any particular $X = x$ will give some evidence about $\theta$ using evidence function, $\operatorname{Ev}(E, x).$ Can anyone explain the intuition behind it with a proper example?