The first thing that we need to know in simple term is the difference between star and planet. Star emit light and are heavy in mass (weight), whereas planets RELATIVELY are MUCH LIGHTER and do not emit light. Most of the planets and stars composition may be the same, but because of the mass, stars at their core develop very high temperature and pressure, which causes fusion to ignite, releasing tremendous amount of energy, which we see as light. Link is provided in the bottom for more information.
And now the question: Is Saturn a Planet or a Star?
We and our children are being taught in school that Saturn is a planet spinning very fast on its own axis, while ancient Hindu books say that Saturn is the son of Star Sun. Obviously this honor has not been bestowed to other planets. The question then arises, is Saturn a star?
Yes as per Hindu belief, Saturn is a star, though some say it is a defective star.
Regarding the defect, there is lot of stories, but they are actually meant to make readers understand the various attributes of Saturn, as per Vedant Jyotish, so they may not be relevant here. However it is accepted by all followers of Sanatan Dharm that Saturn is the son of Star Sun and we can correctly conclude that means that Saturn is a Star, maybe a defective one.