Ravan was the king of Rakshasas. He is said to have ten heads. But he was not born with 10 heads. As per the legends, Ravan performed an intense penance - tapasya - to appease Lord Brahma, which lasted for several years. As a sacrifice and to appease his Lord, Ravan chopped off his head 10 times. A new head arose each time and thus he could continue his penance. At last, Lord Brahma, was pleased with his severe austerity, offered him a boon. Brahma refused Ravan for immortality but gave him the celestial nectar of immortality, which was stored under his navel.
Looking at the intellectual stature of Ravan, his ten heads symbolise the six Shastras and four Vedas, making him a great scholar and the most intelligent person of his time.