Question

who are Sri Lankan Tamils and Indian Tamils

Answer 1

Sri Lankan Tamils are those who are the resident of srilankans only and Indian Tamils are those who came from India for fishing and other activities in Sri Lanka

Answer 2

The native Tamils of Sri Lanka are called Sri Lankan Tamils.
The Tamils whose forefathers came from India as plantation workers during the colonial period are called Indian Tamils.