NRO accounts are Indian rupee accounts that function much like resident savings accounts. Interest earnings in NRO accounts are taxable in India. Repatriation upto USD 1 million (check this) per year are permitted from NRO accounts.
If you are a tax resident in India, we recommend you consult a tax accountant on re-designating your NRE and NRO accounts to resident Indian accounts.
A detailed description is available from the Reserve Bank of India’s website