Audio Noob Question...Help?

I am wondering wats a decent amount of watts for speakers i was looking at kicker and pioneer and im seeing 150watts...why are boxes have a lot more watts and the prices are that dramatic compared...also if it better to have 1 sub or 2 or does it not matter? Do i need a tweeter?Whats a tweeter? Wats a 2 channel amp mean and all that

for wattage, look at the RMS wattage. this is the wattage the speaker can take continuously.

a tweeter is for your highs

a 2 channel amp is simply that. 2 channels.