Relays, what are they and when are they needed?

[jonsamson]

I have recently installed running lights. I didn't want them to come on when I changed to high or when the key is turned on until the starter is hit. I wired one of the wires off the wire that goes direclty to the head light and another to the extra ground in the housing. I works as I wanted it to. But am I asking for trouble eventually?

I assume relays can be bought at Radio Shack, but how do we know what to buy for the application?

Can a relay be changed when changing blinkers to LED's without buying the extra electronics that draw as much as regular bulb thus defeating the purpose of the the lower draws for LED's

What is the basic's of how these little things work?

Why is the sky blue?

Why is it still cold that we can't ride comfortabley,

Opps sorry, got carried away with questions, I was on a role and didn't want to stop. :)

Thanks,
-Jon