Functional Bowel Disorders (FBDs) are a spectrum of chronic gastrointestinal disorders characterized by symptoms such as abdominal pain, bloating, distension, and bowel habit abnormalities. FBDs can be classified into five categories: irritable bowel syndrome (IBS), functional constipation (FC), functional diarrhea (FDr), functional abdominal bloating/distension (FAB/D), and unspecified FBD (U-FBD). The classification acknowledges significant overlap among these categories, and the disorders can be conceptualized as distinct conditions, distinct pathophysiologic conditions, or a spectrum of overlapping disorders. The diagnosis of IBS involves meeting specific criteria, including recurrent abdominal pain associated with defecation or changes in bowel habits. The prevalence of IBS varies by country and demographic factors, with higher rates in women and younger individuals. IBS is divided into subtypes based on predominant bowel habits: IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), and IBS with mixed bowel habits (IBS-M). The diagnosis of IBS should be made based on clinical history, physical examination, minimal laboratory tests, and appropriate diagnostic procedures. The pathophysiology of IBS is multifactorial, involving genetic, environmental, and psychosocial factors. Key mechanisms include altered gastrointestinal motility, visceral hypersensitivity, abnormal intestinal permeability, and immune dysfunction. Stressful life events and post-infectious IBS (PI-IBS) following gastrointestinal infections are also significant contributors to IBS development. The role of diet, particularly gluten, in IBS is a topic of ongoing research, with some patients reporting relief from symptoms on a gluten-free diet.Functional Bowel Disorders (FBDs) are a spectrum of chronic gastrointestinal disorders characterized by symptoms such as abdominal pain, bloating, distension, and bowel habit abnormalities. FBDs can be classified into five categories: irritable bowel syndrome (IBS), functional constipation (FC), functional diarrhea (FDr), functional abdominal bloating/distension (FAB/D), and unspecified FBD (U-FBD). The classification acknowledges significant overlap among these categories, and the disorders can be conceptualized as distinct conditions, distinct pathophysiologic conditions, or a spectrum of overlapping disorders. The diagnosis of IBS involves meeting specific criteria, including recurrent abdominal pain associated with defecation or changes in bowel habits. The prevalence of IBS varies by country and demographic factors, with higher rates in women and younger individuals. IBS is divided into subtypes based on predominant bowel habits: IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), and IBS with mixed bowel habits (IBS-M). The diagnosis of IBS should be made based on clinical history, physical examination, minimal laboratory tests, and appropriate diagnostic procedures. The pathophysiology of IBS is multifactorial, involving genetic, environmental, and psychosocial factors. Key mechanisms include altered gastrointestinal motility, visceral hypersensitivity, abnormal intestinal permeability, and immune dysfunction. Stressful life events and post-infectious IBS (PI-IBS) following gastrointestinal infections are also significant contributors to IBS development. The role of diet, particularly gluten, in IBS is a topic of ongoing research, with some patients reporting relief from symptoms on a gluten-free diet.