Diabetes is a chronic condition characterized by high levels of sugar (glucose) in the blood. It occurs when the body is unable to produce enough insulin or properly use the insulin it does produce. Insulin is a hormone produced by the pancreas that helps regulate blood sugar levels. There are two main types of diabetes: type 1 diabetes, which typically develops in childhood or adolescence and is caused by a lack of insulin production, and type 2 diabetes, which typically develops in adulthood and is caused by the body's inability to use insulin properly. Other types of diabetes include gestational diabetes (which occurs during pregnancy) and prediabetes (a condition in which blood sugar levels are higher than normal but not high enough to be diagnosed as diabetes). 

Diabetes can lead to a range of complications, including nerve damage, kidney damage, eye damage, and an increased risk of heart disease and stroke. Treatment typically involves a combination of medication, diet and lifestyle changes, and regular monitoring of blood sugar levels.