A-B refers to a simple two-letter combination that can represent various concepts, such as a grading system or a type of classification. In education, an "A-B" grading scale typically indicates a high level of achievement, with "A" representing excellent performance and "B" denoting good performance. In other contexts, A-B can signify a comparison between two items or options, often used in decision-making processes. For example, in marketing, an A-B test compares two versions of a product or advertisement to determine which one performs better, helping businesses make informed choices.