What is Fiber?
While fiber is a carbohydrate, it is digested very differently from sugars. Sugars are broken down into glucose and used for energy (or storage) throughout the body. Fiber passes through the GI tract and helps to regulate bowel movements.
There are two different types of fiber: soluble fiber and insoluble fiber. Like the name suggests. soluble fiber can dissolve in water, whereas insoluble fiber cannot. 
Foods rich in soluble fiber include seeds, nuts, beans, berries, and fibrous vegetables. Foods rich in insoluble fiber include wheat, whole grains, and wheat bran.
Why is Fiber Important?
Fiber is important because it helps regulate bowel movements. Insoluble fiber adds bulk to stool, which can be helpful to individuals with constipation.
Soluble fiber dissolves in water and turns into a gel-like substance in the GI tract. This slows digestion and may help individuals with diarrhea.
High-fiber foods can also help feed healthy bacteria and promote a healthy gut microbiome.