What exactly IS offset, and how do I find it??, Buying Tenzo RS5s- need info on tires 2 Options

[shid]

Ok, offset determines how far your tires stick out from the car. Right? good.

Whats the stock offset measurement on our cars?

What does that mean?

I'm getting Tenzo RS5s 17x7s- whats the offset? Does it even matter on the rim? or is it all in the tire size?

and what tire size is right for our cars when upgrading to 17 inchers? Because I've heard that if you increase the wheel size, but don't decrease the tire size, things like your speedo will be off.

Is the speedometer problem fixable? or is the only way to go with lower profile tires (and get much lower ride quality).

Does upgrading to 17s and decreasing tire size even increase handling? or is it the same?

As for offset recommendations- what do they mean and how do I implant them? I'd like to have the new rims to stick out from the car a LITTLE (I think it looks very rallyish and cool but will that cause rubbing problems?

And whats this about checking break clearance? Is that only needed when going the other direction (more IN to the car)

is going out to less flush with the car a stupid idea? Feel free to tell me so.

I did a search, but all I got was a lot of garbled results. A couple were decent. "Use this and this offset" but I still didn't UNDERSTAND the reasoning behind it.

and whats this about a higher number offset being in closer towards the vehicle?

So confused! Help!~!!