Fiber is an umbrella term that describes two types of carbohydrates made by plants. Insoluble fiber is structural and surrounds a plant cell like the rigid scaffolding around a building. If you add water to insoluble fiber, nothing happens to it (think celery). Soluble fiber is not structural and turns into a mush or gel when water is added (think oatmeal or psyillium) and both types help keep things moving in the intestines. Neither types are digested by humans, but soluble fiber is digested by your gut bacteria and helps provide for a happy biome. Soluble fiber also picks up bile (made of cholesterol) in the gut and prevents it’s reabsorption, thus transporting it out, and regulating our blood cholesterol levels. Insoluble fiber does not dissolve in water, passes through relatively unchanged and simply adds bulk to the larger intestinal contents. Its important to have enough fiber in the diet to keep the intestines happy and moving. For a normal adult female, this is 21-25 g. For a guy, 25-30 g. How much is this? 1.5 C broccoli has 7g. 1 apple has 4.5 g. A head of lettuce has 13g. 2 Tablespoons of Psyllium has 10 g. 1 cup of brussels sprouts 3.3 g. Animal products have ZERO fiber, because animals are not plants.
You can search this site for fiber content of foods: https://www.myfitnesspal.com/food/calorie-chart-nutrition-facts