"Rocky planets" are planets made mostly of solid rock, like Earth. They have a solid surface and are different from gas giants that are mostly made of gases. Full definition
We've got plenty of evidence of rocky planets in the habitable regions of their respective stars. (seeker.com)
Unlike the other rocky planets in our solar system, it has an immense iron core that makes up roughly 70 per cent of the planet's volume. (newscientist.com)
A more appropriate way to put this might be that life will emerge on small rocky planets with a probability of 1 per cent. (newscientist.com)