What are residual power and which level of government has them?

Residual powers refer to the authority to legislate on matters not explicitly assigned to the federal or state governments by a constitution. In the context of the United States, residual powers are primarily held by state governments, as the Tenth Amendment of the U.S. Constitution reserves powers not delegated to the federal government for the states and the people. This allows states to address issues and enact laws that are not covered by federal legislation.