An Ayurvedic Vishesh Massage is similar to an Ayurvedic Abhyanga Oil Massage, but then applied more vigorously, more stimulating and energizing, performed as a real deep tissue massage for muscles and tendons.
The difference with a general Abhyanga Massage is that Vishesh is more suitable for so-called Kapha body types experiencing excess (associated with, for instance, heaviness, hardness, coldness, and slowness), while Abhyanga would be more suitable to balance out excess in Vata body types (associated with dryness, lightness, nervousness, and movement, among other things).
Additionally, Vishesh Massage focuses more on the abdominal area, back, and legs of the receiver, in comparison to Abhyanga Massage. In general, less oil is used during a session compared to the common Abhyanga full body massage.
The health benefits of Vishesh are more or less the same as with Abhyanga. Think of general detoxification, stimulation of the digestive system, alleviation of skin problems, improvement of blood and lymph circulation, stimulation of the immune system, pain relief, nourishing (due to oils used), and relief of stress, anxiety, and tensions.