Karma is one of the most important concepts in Buddhism. Karma is an imprint in one's Mind. When one performs a good deed out of good intentions, the good intentions come from the Mind. Having done that good deed, the residues of these intentions stay in one's Mind as "imprints", and that is "good karma". The opposite goes for evil deeds (or what the Buddha would call "unwholesome deeds") done out of greed, hatred etc. There is a story about a boy whose name is Doudou suffered the pain instead of being sent to hospital:
On June 23, 2008, according to A Story of a Six-Year-Old Practitioner Doudou, "Doudou had to pass the test of illness karma after we came to Korea. She had high fever, her body ached, she had a sore throat and her heart ached too. She cried when she couldn't stand it anymore, but still she's been strong as always." Both her parents are practitioners, so instead of sending the kid to hospital for professional help, they insisted that the girl should "go to take part in the demonstration held on the second day." The parents insisted it was the karma.
Is it true that Doudou had done something bad that she should stand the pain to eliminate karma?