Inflammation is the immunological response of the immune system. Our body's immune system responds to foreign invaders, injured cells, and poisonous substances. When our immune system works well, it cleans up debris, repairs wounds, and drives out alien invaders. However, excessive inflammation may cause a wide range of inflammatory diseases. Inflammation may be a symptom of chronic diseases. Experts believe that inflammation may play a significant role in a wide range of chronic diseases, such as ulcerative colitis, cancer, autoimmune diseases such as rheumatoid arthritis, and neurological disorders. People can be affected by these inflammatory diseases at an early or late stage. Therefore, basic knowledge about these inflammatory diseases may be helpful for management in an efficient manner. The aim of this chapter is to highlight basic knowledge about inflammatory disease, its epidemiology, risk factors associated with inflammatory diseases, and disease pathophysiology.