Inflammatory bowel disease (IBD) can manifest as either Crohn's disease or ulcerative colitis. Crohn's disease causes transmural inflammation that can affect any part of the gastrointestinal tract, most commonly the terminal ileum. Ulcerative colitis only involves the colon and rectum in a continuous pattern. Both diseases present with diarrhea, abdominal pain, and possible extraintestinal symptoms. Diagnosis involves endoscopy and biopsy to distinguish between the two based on involvement patterns and disease characteristics. Complications can include strictures, fistulas, abscesses, and increased cancer risk if the conditions are not well controlled.