Bt cotton is an example of genetically modified organism.

no

Genetically modified food is created in a lab by removing a gene from one organism and forcing it into an organism of a different species.

Genetically modified organisms are modified on a genetic level to benefit humans. How this can pose a threat to a population or ecosystem, is that if the genetically modified organism were to somehow create a mutation, and pass that on, it could be damaging to the future generations in reducing their health or other issues may arise. It can also be damaging to an ecosystem if a genetically modified organism were to escape into a wild population and change it.

GMO stands for a Genetically Modified Organism.