From the Summary: "On March 13, 2020, President Donald J. Trump declared an emergency under Section 501(b) of the Robert T. Stafford Disaster Relief and Emergency Assistance Act (Stafford Act; 42 U.S.C. §§5121 et seq.) in response to coronavirus disease 2019 (COVID-19). The declaration authorized assistance to all U.S. states, territories, tribes, and the District of Columbia. [...] This report provides answers to frequently asked questions (FAQs) regarding the Stafford Act disaster declarations made for COVID-19, federally available assistance, and sources of funding."
CRS Report for Congress, R46326
Congressional Research Service: https://crsreports.congress.gov/