A logic error occurs when a program runs without crashing but produces incorrect results due to flawed reasoning in the code. These errors often stem from incorrect assumptions or mistakes in the algorithm, leading to unexpected behavior. For example, if a programmer intends to calculate the average of a set of numbers but mistakenly sums them incorrectly, the output will be wrong, even though the program executes smoothly. Identifying logic errors can be challenging because they do not generate error messages like syntax errors do. Debugging tools and careful code review are essential for finding these issues. Programmers often use test cases to verify that their code behaves as expected and to catch any logic errors before deployment.