Here is an example to understand karma. This is a pretty elementary model, but gives the general idea of karma:
A deer is standing in the woods. In his past life the deer was a man who shot and killed an animal. He wears a sign that says "Shoot Me." A hunter is walking by and sees the sign. He shoots the deer, and goes over and picks up the "Shoot Me" sign and puts it on himself.
He wears this sign the rest of his life. In a few years the hunter dies. When his soul leaves his body, the subtle material body (false ego, etc. accompanies it) and takes along with it the "Shoot Me" sign.
The subtle body and soul take on the gross material body of a deer. The new deer now wears the "Shoot Me" sign. Along comes a hunter and shoots the deer. He goes over and picks up the "Shoot Me" sign and puts it on himself.
And so on.
The point is: it was the deer's karma to get shot. Nevertheless, the hunter is still incurring karma for killing the deer.
The way to break the endless material cycle of suffering is to meditate/chant the names of the Lord from our recommended mantras. . That is part of the effectiveness of Mantra Meditation, changing a person's karma.
