There are three main schools of Tantra: Mishra Tantra, Kaula Tantra and Samaja Tantra.
Samaja Tantra
Samaja Tantra is also called "the right-hand path". Adepts of Samaja Tantra practice meditation on the Sahasrara chakra. They also learn about chakras nadis and pranas.
Mishra Tantra
Adepts of Mishra Tantra practice meditation and physical practices the aim of which is to open the Anahata chakra.
Kaula Tantra
Kaula Tantra is also called the "left-hand path". Adepts of Kaula Tantra meditate upon the Kundalini force. They make use of outer (usually physical) practices to open the Muladhara chakra.