Tarabalam is good time in a day for a particular nakshatra. Chandrabalam is good time in a day for a particular rashi. Tarabalam is widely followed by people. Chandrabalam is not used widely. Tarabalam is the important one as per most astrologers.
Tarabalam is mainly followed in South India, especially in Andhra Pradesh, Telangana, Karnataka and by some communities in Tamil Nadu and Kerala.
Chandrabalam is widely used in North Indian astrology and prominence here is given to rashi. Tarabalam is rarely used in North India.