If a domain is not renewed before the expiry date is reached, it enters what is commonly referred to as the Grace Period. The Grace Period typically lasts between 0 and 30 days and often does not have any additional costs associated with it allowing a domain name to still be renewed at the normal rate.
When the grace period elapses, most domains then enter a status of Redemption. Redemption is the last chance to renew a domain before it becomes available for registration again and often coincides with registries putting the domain up for auction. Domains can still be renewed while in the redemption status (providing it hasn't been auctioned off) by paying a redemption fee plus the regular renewal cost for the domain.
If a domain is still not renewed after this time, then the domain is "released" and becomes available for new purchases again.
