The Praying Mantis is a predatory insect with nearly 2,000 species around the world. According to many experts, the mantis is closely related to cockroaches. Other relatives commonly sited are stick insects and grasshoppers.
The adult praying mantis ranges in size from a centimeter to several inches in length. They feed upon many pest insects and are, therefore, beneficial garden residents.
Despite their large size, spiked bodies and predatory nature, the mantis shouldn't be considered a danger to humans. Although related to the cockroach, the mantis is not a known vector for human pathogens. I have read of a couple occassions of mantids biting humans, but it is probably rare; the danger of such a bite is probably limited to those who happen to be allergic to the mantis itself--a diagnosis of which is probably even rarer.
I have handled several dozen wild mantids in my life. None have shown signs of aggression. Generally speaking, the mantis will try to flee by hopping or flying away.