What makes a champion
A champion is more than a friendly contact. They have a personal or professional reason for wanting the change, they have influence with the people who will decide, and they are willing to use that influence for you. They share information you couldn't get otherwise, such as who else is involved, what the competition is offering and what the economic buyer cares about. A contact who likes you but can't or won't do those things is a coach at best, not a champion.
Example
An operations manager who has fought manual reporting for a year shares the internal approval process with the rep, introduces him to the finance lead, and forwards the rep's one-page summary to her director with her own note of support. That's a champion.
Why it matters
Most of a buying decision happens in meetings the seller never attends. A champion carries your message into those meetings, answers objections on your behalf and warns you early when something changes. Deals without one tend to stall or end in no decision. MEDDPICC includes the champion as one of its core elements for this reason, and many teams test whether a supposed champion has actually done something for the deal.
How to practice it
Practice the questions that test a champion: 'What would this change mean for you personally?', 'Who else needs to be convinced?' and 'Would you be willing to set up a call with them?' Rehearse coaching a champion to present your case internally, including the questions their boss is likely to ask. Practice handling the moment a champion goes quiet, too, because that is often when a deal is at risk.