A Condorcet method is any election method that elects the candidate that would win by majority rule in all pairings against the other candidates, whenever one of the candidates has that property. A candidate with that property is called a Condorcet winner
A Condorcet winner doesn’t always exist because majority preferences can be like rock/paper/scissors: for each candidate, there can be another that is preferred by some majority (this is known as Condorcet paradox). Voting methods that always elect the Condorcet winner (when one exists) are the ones that satisfy the Condorcet criterion.
Most Condorcet methods have a single round of voting, in which each voter ranks the candidates from top to bottom. A voter’s ranking is often called his/her order of preference, although it may not
match his/her sincere order of preference since voters are free to rank in any order they choose and may have strategic reasons to misrepresent preferences.