Bilinear maps and non-degeneracy

Question

Let $\mathbb{G}_0$ and $\mathbb{G}_1$ be two multiplicative cyclic groups of prime order $p$, $g$ a generator of $\mathbb{G}_0$ and $e$ a bilinear map, $e:\mathbb{G}_0\times\mathbb{G}_0\rightarrow\mathbb{G}_1$. The bilinear map $e$ has the following properties:

1. Bilinearity: for all $u,v\in\mathbb{G}_0$ e $a,b\in\mathbb{Z}_p$, we have $e(u^a,v^b)=e(u,v)^{ab}$
2. Non-degeneracy: $e(g,g) \neq 1$

I don't understand the second property (non-degenerancy). Why $e(g,g)\neq 1$ ? (I don't understand $\neq 1$).