calculus - Confusion around $lim_{x to 0}frac{sin x}{x}, sin x/x,sin 0/0$

Recently in my calculus class I have been taught $\lim_{x\to 0}\frac{\sin x}{x}$ =1. Now, in trigonometry I have studied $\sin 0=0$. Also, I don't see $\sin x/x=1$. Now my confusion is that if I have to use these identities in some practical applications , which of them should I use?