Net carbs
Total carbohydrate minus fiber: an estimate of the carbs that raise your glucose.
Net carbs subtract fiber (and, on some labels, sugar alcohols) from total carbohydrate, because fiber passes through largely undigested and has little effect on blood glucose. The idea is to count only the carbohydrate your body turns into glucose.
It's a useful shorthand: a high-fiber food with 30 g of carbohydrate and 12 g of fiber behaves more like 18 g, and it's why we rank restaurant menus by net carbs. It's an estimate, not an exact science, so your own post-meal reading is still the best check.