What's the different between kusala (good) and akusala (bad)?

What's the different between [ku-sala](http://accesstoinsight.eu/en/dictionary/kusala) (good) and [a-ku-sala](http://accesstoinsight.eu/en/dictionary/kusala) (bad), in regard of what the Buddha taught? *(ku - bad, sala - cutting away, a - not)* What are good and bad actions by deeds, speech and mind, and what qualities defines them as such? `Here he grieves he grieves hereafter. In both worlds the wrong-doer grieves. He grieves, he's afflicted, seeing the corruption of his deeds.` `Here he rejoices he rejoices hereafter. In both worlds the merit-maker rejoices. He rejoices, is jubilant, seeing the purity of his deeds.` [Yamakavagga](http://www.zugangzureinsicht.org/html/tipitaka/kn/dhp/dhp.01.bpit_en.html#s-dhp-16) So good to now really good of how to distinguish and alltime worthy to ask, remember and tell for many's benefit, and the own. *(Note that this is not asked/given for trade, exchange, stacks or entertainment but as a means to escape this wheel here)*