Embedding a $deg \geq 4$ curve in $\mathbb{P}^2$

Question

Reading the paper by Kollar "The structure of algebraic threefolds", among some examples he does talking about intrinsic and extrinsic geometry over $\mathbb{C}$, he mentions that "an irreducible curve of degree at least 4 can fit into $\mathbb{P}^2$ in only one way".

I know some basic things about curves, but I don't see this fact. How to prove it?