Officially starts from 100 and they are not idiots, because they just learned how the pieces move and don't all of us were idiots and learned how pieces move at first?
What's the FIDE rating of a baby?

I've seen players here with 140 rating , some 230 ratings etc .. nothing wrong with it , nothing to be embarrassed you just need to learn that's it

It's just a maths formula, it's not like measuring someone's height.
So you take, lets say, a 1000 rated player. There are conceivably players who would only win 1 out of 4 against this person. 1 out of 4 relates to about 200 points difference, so a rating of 800. Then there are players who would lose to this person 3 out of 4 and so on. Stepping backward through the ratings like this, the worst imaginable player would have a negative rating. Some young children would probably be negative right after learning the rules. The rating systems I know of though don't let ratings fall below a certain number, like 100.
A baby wouldn't have a rating, because a baby can't learn the rules.
Basically, what rating would someone have if they had literally 0 idea how to play? Put another way, what's the lowest feasible rating number? I hear it's very rare for anyone to drop below 300, but surely at least theoretical idiots exist down there?