Line Conditioner - meant to "clean" and "condition" the household current to recover a smooth 60hz cycle from impurities. (am no believer in this hype.)
Surge Protector - meant to protect the connected appliance from electrical transients caused by lighting or resumption from power outages which can be deleterious to sensitive gear.
Power Strip - another term for power extension cord
Automatic Voltage Regulator - as the name suggests, it regulates the AC voltages to stay within a tigher tolerance, preventing huge swings above or below the required 220 or 110 voltages common in some areas.
A google search will yield a more thorough explanation of each.
