The term "Cargil war" seems to refer to the Kargil War, which took place between May and July 1999. It was a conflict between India and Pakistan over the disputed Kargil district in the Indian-administered region of Jammu and Kashmir. The war began when Pakistani soldiers and militants infiltrated the high-altitude regions of Kargil, leading to intense fighting with Indian forces. The conflict ended with India regaining control of the territory and a return to the status quo along the Line of Control (LoC). 

For a 6th-grade level explanation, you might say:

The Kargil War was a fight between India and Pakistan in 1999. Pakistani soldiers sneaked into a part of India called Kargil, which is in the mountains. India and Pakistan had a lot of fighting, but in the end, India took back control of the area.