Machine learning models don't do well with math that has hard bounds at 1 and 0 (probability). So we use the log of the odds ratio instead. This function goes from negative infinity to positive infinity. And is mappable back to 0 and 1. So as you get closer to infinity log odds, you get closer to 100% certainty that your answer is A.
It's just ln(p/(1-p)) under the hood.