Some special subjects which are not included under state list, concurrent list and central list . These subjects are decided by central government. This is called residuary power. Example: subjects related to computer.
matter which are not included in the division of power.
Residuary powers of legislation.-(1) Parliament has exclusive power to make any law with respect to any matter not enumerated in the Concurrent List or State List.(2) Such power shall include the power of making any law imposing a tax not mentioned in either of those Lists.
Sunjects in residuary list are controlled by the central government….such as computer

Parliament has exclusive power to make with respect to any matter not enumerated in concurrent or state list

The subjects which came up after the Indian constitution was made are called residuary subjects . Eg :- computer software, Information technology etc . According to the Indian constitution the central government has the power to legislate on these subjects