An invasive species is defined by any species that is introduced to a region or ecosystem by unnatural means (particularly human actions). They are generally known to cause many ecological and economical problems and are extremely difficult to remove. Many approaches of removing invasive species, including introducing predators and the use of toxins and poisons, are generally unsafe and harmful and threaten to increase the problem.
Exotic species are in many ways, very similar to invasive species. Exotic species can be displaced accidentally or intentionally by humans, or they may be naturally be placed into their new habitat. Unlike invasive species, they may not create harm the the environment they are introduced to. Because the term exotic species is more general than invasive species, all invasive species are also exotic species. However not all exotic species are invasive.