Gliese 581c (or Gl581c) is a planet 20 light years away orbiting the red dwarf star GLIESE 581. It was the first reported potentially Earth-like planet that could be capable of supporting life! But with further research it seems that the environment would probably be too unstable for us because the planet is tidally locked. Since same side is always facing the sun its conditions are more likely to be very similar to Venus rather than Earth.
However, research speculates that Gl 581c could technically be habitable as long as it is always kept in specific conditions; This was a research project imagining what human life of Gliese 581c could look like if we kept the planet in the state we would need it in.