Crohn’s disease belongs to a group of conditions known as inflammatory bowel diseases, or IBD. Crohn’s disease is an inflammatory bowel disease that causes chronic inflammation of the gastrointestinal tract. It can affect any part of the GI tract from the mouth to the anus and can affect the entire thickness of the bowel wall. Inflammation of the intestine can "skip," or leave normal areas in between patches of diseased intestine. 

The most common symptoms of Crohn's disease include abdominal pain, tiredness, increased bowel movements, nausea, bloating, fevers, joint pain, loss of appetite, and weight loss.

References:

1. https://www.crohnscolitisfoundation.org/what-is-crohns-disease/overview