Explain the condition called childhood diabetes.

Not accepted term. I assume you are referring to type 1 diabetes, which is an autoimmune disorder, in which the body makes antibodies against its own Insulin producing cells. These patients can only be treated with insulin. We don't use "childhood" or "juvenile" diabetes anymore because children can get type 2, which is due to Insulin resistance usually from being overweight, and adults can get type 1.
Childhood diabetes. In this day and age, some child now can have type 2 diabetes due to obesity so the term childhood diabetes doesn't tell much anymore. The better term now is insulin-dependent or insulin-independent diabetes.
Dated. Before the current obesity epidemic, diabetes that started in childhood was usually type 1, which may be caused by autoimmunity. However, with the current problems with childhood obesity, many young kids being diagnosed with diabetes are actually type 2, which is caused by obesity and genetics. 'childhood diabetes' is a dated term that is prob not helpful at distinguishing the type anymore.
Inherited mostly. It is also called "juvenile" or "childhood" diabetes because it often emerges in a patient's early years.