It doesn't make sense to talk about an individual graph being non-isomorphic. Informally, two graphs are non-isomorphic if they are structurally different.
If we have two graphs $G_1$ and $G_2$, then if $G_1$ is bipartite and $G_2$ is not bipartite, then they are non-isomorphic. (I'm guessing this is the link between the two topics you've encountered.)
If they instead both happen to be bipartite, they may or may not be isomorphic. E.g. $C_8$ and $C_4 \cup C_4$ are two non-isomorphic bipartite graphs.
Graph isomorphism testing is a non-trivial problem, and is often practically solved computationally.