170 watts is the amount of power "wattage" that your speakers will output..
RMS watt's are what the speaker could run on all day every day..
MAX watts is what it'll peak up every now and then... make sure you check the RMS value (should be on the side of the box)
3 way, means theres 3 different speakers inside the 1 speaker
if they're 6" it'll be mids, and 2 tweeters.. or if its a 6x9 it'll be one low, one mid, one tweet.
the higher the wattage, the more powerfull.. but 170watt peak will only be around 85watt RMS... the really good brands will show their RMS ratting on the front, the crappier brands and the low end pioneer, sony stuff will just have the peak watt's to try sucker people in!
hope this helps... does i just make sense?