What they are
Evaluation criteria are the stated dimensions on which the options in a selection (vendors, proposals, investment options, candidates) will be judged, usually with weightings that convert individual judgements into a comparable score. A typical procurement set covers capability, approach, team, commercials, risk and cultural fit, with the weightings summing to a scoring model.
Why they matter more than the scores
Weightings are the decision. Set price at 40 per cent and you have chosen the cheap bid before opening an envelope; set transformation experience at 25 per cent and you have chosen the large incumbent. Neither is wrong, but both are choices, and they deserve the scrutiny the scoring meeting gets. The discipline that protects the outcome is sequence: criteria and weightings agreed, in writing, before responses arrive. Agreed afterwards, they become a justification engine for whichever option the room already prefers.