Why is total resistance lower in parallel circuits and what does it do?

[Teachme]

I am just wondering about the total resistance or a parallel circuit. I know that the total resistance of a parallel series is always less then the lowest component of the circuit.

What would you use this information for though and how is it useful? Also does the low total resistance have any effect on the system?

 

[NascentOxygen]

The lighting circuits in your house are parallel circuits. The more lights you have on, the more expensive your power bill!

 

[rktpro]

When you have high resistors and you desire a lower resistance, you use this combination. (Only possible when you are working in junkyard or a 1200 AD lab)

Effective resistance helps you know the current passing through the junction. What if you were planning to attach an iron somewhere and you don't know the wattage and the current in the circuit. If current flowing is larger than required, you going to burn that.
These basics have made the pillars of modern physics. Even the keyboard you use to type has been made with one such principle. Ohm's law requires effective resistance.