Back in the old days of lulz, us druids didn't benefit from weapon DPS at all. All we cared about were stats. Whether the weapon had 100 DPS or 90 DPS, we didn't really care.
Then came along Blizzard and felt that we weren't exactly scaling as well, so they buffed us up by adding feral attack power to every item. Only druids can see it and it's based on the weapon's DPS, as far as I know.
If you see a polearm with +100 attack power and say +1500 feral attack power, it will give you a total of 1600 attack power - 100 in caster + 1500 in bear/cat. However, if a hunter equips it, it will only give him 100 attack power.
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Please "talk up" if your comprehension white-shifts. I will use simple-happy language-words to help you understand.