There are several different stories about these children, but all are similar. In every story a girl of about ten years old with a boy of a few years younger were found at the mouth of a cave dressed in clothes that were unknown to anyone. Some described their clothing as being made of a strange metallic cloth. Their skin was green and the villagers that found them said that the language they spoke was like no other they had ever heard before.
The story of the "green children" has intrigued me since childhood. This article goes into considerable detail about what little is known and what remains conjecture.