That’s basically a generic (and grammatically incorrect) term for fiber-rich carbs that don’t greatly cause a spike in blood sugar/glucose. In a nutshell, fiber-rich foods fall into this category, and back in the low-carb fanaticism days, foods often listed total carbs and net carbs. Fiber isn’t digested in the small intestine and so isn’t broken down into glucose and absorbed into the blood.
But this practice is somewhat questionable, because things like Atkins chocolate bars started not counting sugar alcohols and questionable things like that toward the carb count. So today it’s not really a good method to use. Just know that beans, veggies, etc. may contain carbs but those don’t impact insulin like, say, carbs from pasta. “A carb is not a carb” as the saying goes. It’s all about good food selection in the end.