Here is a great explanation from the Maine Secretary of State:

This May 2018 animation explains how ranked-choice voting will work in Maine elections. The State of Maine will be the first state in the nation to use RCV in a statewide election, for the June 12, 2018 Primary Election. For additional resources and information about ranked-choice voting, visit our RCV Resources webpage at http://www.maine.gov/sos/cec/elec/upc….