After a bit of investigating, I found the following information pretty interesting and useful to those registering and renewing domains:
Domains are registered for a period of one or more years.
After the registration period has elapsed, the owner can renew the domain for the cost of the domain alone.
However, if you are unable to renew the domain by the expiry date, you have 19 days to renew the domain using a verified credit card (paypal is accepted, but it must be linked to a legitimate credit card).
After 19 days past the expiry of your domain, GoDaddy will charge you an $80 redemption fee, which is basically their way of squeezing every last dollar from a forgetful webmaster. You then have about 5-10 days to redeem it at the cost of the domain + the $80 fee.
After the redemption period is over, your domain will be put up for sale for the highest bidder. At this point, you're pretty much out of luck - as you'll have to compete against the global marketplace and GoDaddy to take back possession of your domain.
That in a nutshell is GoDaddy's policy on domains. Interesting that you have 19 days past the expiry to renew, with no extra fee.