What is fiber? What is dietary fiber? 

Fiber is also known as roughage. It is the indigestible part of plant foods that pushes through our digestive system, absorbing water along the way and easing bowel movements.

The word fiber (North American) can also be spelled fibre (British). It comes from the Latin word fibra, meaning fiber, thread, string, filament, entrails. Dietary fiber refers to nutrients in the diet that are not digested by gastrointestinal enzymes.

Fiber is made up of non-starch polysaccharides, such as cellulose, dextrins, inulin, lignin, chitins, pectins, beta-glucans, waxes and oligosaccharides. The word fiber is misleading, because many types of dietary fibers are not fibers at all.
There are two broad types of fiber, soluble and insoluble.
Soluble fiber dissolves in water. It changes as it goes through the digestive tract, where it is fermented by bacteria. As it absorbs water it becomes gelatinous.
Insoluble fiber does not dissolve in water. As it goes through the digestive tract it does not change its form.
Dietary fiber foods are generally divided into predominantly soluble or insoluble.
Both types of fiber are present in all plant foods, but rarely in equal proportions.
Courtesy;;EASTERN PANACEA.