@poppeacock a Condorcet method is defined in terms of the notion of a “Condorcet winner”, which is a candidate that beats every other candidate in a majoritarian head-to-head match up, also called a “beats all” winner. There can be at most one Condorcet winner in an election; however, there are pathological cases when a Condorcet winner does not exist at all, caused by what are known as Condorcet cycles.
The classic example is three voters using rank ballots over three candidates:
V1: A>B>C
V2: B>C>A
V3: C>A>B
You can see that A>B 2:1, B>C 2:1, but C>A 2:1. So A>B>C>A is a Condorcet cycle, which is a generalized “rock-paper-scissors” situation. Whichever candidate you choose as the winner, there is some majority of the voters who would have preferred a different candidate. That’s the unfortunate thing that happens when a Condorcet winner doesn’t exist…
Regardless, a Condorcet method is any method that guarantees electing the Condorcet winner when one exists. Condorcet methods differ in how they reconcile choosing a winner when the Condorcet winner does not exist, I.e. in effect how they determine which majority group(s) to jilt.
So for example, if Ranked Robin doesn’t specify how it resolves when there is no Condorcet winner, then it’s really a blanket term for Condorcet methods in general. Or maybe it’s a label for a particular curated subset of Condorcet methods.
There are many Condorcet methods, including Ranked Pairs, Schulze’s method, Copeland’s method, Minimax, and Bottom-Two-Runoff (by Tideman).
I like Bottom-Two-Runoff because it’s efficient and also equivalent to a seemingly (but not actually) more robust system: https://www.votingtheory.org/forum/topic/564/bottom-n-and-bottom-2-runoffs-are-equivalent
