Programmers often discover solutions while explaining a problem to someone else, even to people with no programming knowledge. Describing the code, and comparing to what it actually does, exposes inconsistencies. Explaining a subject also forces the programmer to look at it from new perspectives and can provide a deeper understanding.
No. Brainstorming is when you’re with a group and everyone is throwing out ideas unfiltered.
Rubber duck debugging is when you are trying to solve an issue by describing your problem to another person (or a rubber duck) and through the act of describing the problem you gain a better understanding of the issue and often this causes you to get a ‘eureka moment’ where the solution is suddenly clear to you.