How does address verification work?

[Silverbug]

I just implemented a cc gateway to a site, and when processing credit cards how does it validate the address?

I mean to verify the address, the address entered and sent to the gateway would have to exactly match the address at the bank/cc company. Or does it just do some sort of comparison?

[Brangwyn]

You'll get an AVS decline if it doesn't match exactly whats pinted on the customers CC statement basically.