In biology, what is Handicap Principle?

This refers to a hypothesis which states that members of a species might develop features that at first seem to expose their biological weakness in order to actually signal their strength. This principle has been used to explain why the peacock, for instance, developed a colourful but cumbersome tail even though it reduced the bird’s chances of survival. The hypothesis states that the cumbersome tail might actually signal biological strength as the peacock manages to survive despite the size of its tail. The idea was proposed by Israeli biologists Amotz and Avishag Zahavi.