Kidney disease, also known as renal disease, refers to conditions that impair kidney function. The kidneys are vital organs responsible for filtering waste products from the blood, regulating fluid balance, and maintaining electrolyte levels. Chronic Kidney Disease (CKD) is a long-term condition characterized by a gradual loss of kidney function over time. It can be caused by diabetes, high blood pressure, glomerulonephritis, and polycystic kidney disease. Symptoms often include fatigue, swelling in the legs and ankles, shortness of breath, and changes in urination patterns. Early detection through blood and urine tests is crucial, as the disease can progress to End-Stage Renal Disease (ESRD), requiring dialysis or a kidney transplant. Preventive measures include managing underlying conditions, maintaining a healthy diet, regular exercise, and avoiding nephrotoxic substances. Effective management can slow the progression and improve the quality of life for those affected. This book outlines the processes and mechanisms in the kidney in detail. This book will also provide interesting topics for research which interested readers can take up. In this book, using examples, constant effort has been made to make the understanding of the difficult concepts of kidney diseases as easy and informative as possible, for the readers.