Buddha Abhidhamma - Ultimate Science - BuddhaNet

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Four Kinds of Kamma (Kamma-catukka)
Kamma, Sanskrit karma, literally means volitional action or deed.
As a rule good actions bear good results and bad actions bear
bad results.
Now action may be performed by bodily movement (kàya),
by words of mouth (vacã), or by thought (mano). But the body
and the mouth cannot move on their own accord; they have to
be moved by the mind (citta) through cittaja-råpa.
Again citta is just the awareness of a sense-object; it does
not give the order or direction to perform an action on its own
accord. It is the volition (cetanà) which directs the citta and its
concomitants to perform the action. So cetanà is responsible for
carrying out an action.
Thus, strictly speaking, kamma means all moral and immoral
volition (cetanà). The volition having the root in ignorance (moha),
greed or attachment (lobha) or anger (dosa) is evil. The volition,
which is accompanied by generosity (alobha), good-will (adosa)
and wisdom (pa¤¤à), is wholesome.
In other words, the cetanà present in the 12 akusala cittas are
immoral kammas whereas the cetanà present in 8 mahà-kusala
cittas, 5 råpàvacara-kusala cittas and 4 aråpàvacara-kusala cittas are
moral kammas.
Now cetanà and its concomitants (i.e. citta and cetasikas other
than cetanà) perish after performing their respective purposes.
But before they perish, they leave their kammic property in the
citta-stream. This kammic property is the potential kamma which
will produce its due effect in some proper time, and the effect
will fall on the doer himself.
It is somewhat analogous to Newton’s third law of motion
in physics. The law states: “To every action, there is an equal