@Arbre Carbohydrates comprise a spectrum of sugar molecules from the simple, glucose (most easily digestible), to the complex, cellulose (totally indigestible). The more any specific carbohydrate resembles glucose and the less it resembles cellulose, the more easily and quickly it digests and affects blood glucose and insulin (higher glycemic load). The more it resembles cellulose and the less it resembles glucose, the more effort and time it takes to digest and affects blood glucose and insulin more slowly (lower glycemic load). [Source]
Most foods containing significant carbohydrates contain a mix of many different saccharide molecules. This complicates exactly how the food (rather than the specific saccharides) affect the glycemic load. [Source] How much and how fast any specific food affects blood glucose and insulin is important. Your metabolism can deal with ‘low and slow’ better than ‘high and fast’.