Karma refers to the law of cause and effect - that every action will have a reaction. When we act selfishly or unethically, we become eligible for punishment in the form of negative reactions. However, if we act according to religious instructions and please God, we will not fear reactions.
The lesson discusses how one can remain engaged in normal activities like work or study while being Krishna conscious. It states that we do not need to abandon our positions, but should chant Hare Krishna and dedicate our work to Krishna's service. When we offer our work to Krishna with devotion, it becomes free from reactions.
A story is told of a boy who painted on a wall and avoided