I'm taking this Coursera's course on Graph Theory, which is part of a specialization in discrete math for CS, offered by University of California, San Diego: https://www.coursera.org/specializations/discrete-mathematics
In this course they state this theorem:
An undirected graph $G(V,E)$ has at least $|V|-|E|$ connected components.
With the proviso that if $|E|>|V|$, then |V|-|E| will be negative, so, despite of still being true, it will be kind of useless.
Looking for further information on this theorem, I don't find it anywhere else on the web, so I want you guys to tell me if this is a correct theorem, because for some reason I find it "weird".