Terms Used:

Benefic -- A planet which easily produces results which would be generally considered favorable or "good." Whether these results really are good for the native will only become clear over time. Certainly benefics produce a desired result more easily in most situations than malefics (see next entry). The natural benefics are Venus, Jupiter, the Sun by trine or sextile aspects, and any planet that is well aspected and dignified (see note). Malefic -- A planet which does not easily produce results which would be considered "good". Generally speaking malefics are not so much "bad" as it is that they require more thought, more consciousness, and more skill at managing life than the benefics require in most cases. In fact the two main malefics, Mars and Saturn, are necessary for building character and strength. But either of these handled without consciousness leads to less than fortunate results. The natural malefics are Mars, Saturn and the Sun by conjunction only. General Comment about Both Benefics and Malefics -- Ultimately whether a planet is a malefic or a benefic depends upon a number of factors. Planets that are naturally one or the other can be converted into their opposite by other circumstances in the chart. One cannot assume that Venus and Jupiter will always produce good results, and that Saturn and Mars will always produce bad results. This is a old classification and must be taken somewhat freely. In the end I like Ptolemy's definition of the terms best. According to Ptolemy, a benefic is a planet whose natural influence leads to moderation and balance. A malefic is a planet whose natural influence leads to extremes and imbalance.