Domain is the most important thing on internet. Everyday thousands of domain names are registered and thousands are expired. The other interesting fact is that domain has its own life cycle. Every domain goes through the various phases. Did you ever wonder about the life cycle of a domain name. Are you interested in knowing. Here it is, I am writing the phases of a domain in sequential order:-

Available
This is the first phase of the domain name life cycle. A domain name is available to the public for registration for a period not to exceed a maximum term of 10 years. A user can only register a domain name for a period of 10 years. However after 10 years he can again extend the registration for another 10 years, of course if he is interested. Cost of domain registration varies from registrar to registrar.

Active
Once the domain name is registered it comes in active state and can be renewed for a period not to exceed a maximum of 10 years.
Expired
If the domain is not renewed on or before its expiry date, the domain name is expired. All services related to domain name ceases. Expired state generally ranges from 0-40 days. However if the domain is not renewed by the owner during this phase, the domain goes into redemption period phase.
Redemption Period
Redemption period generally lasts for 30 days during which the domain can still be renewed by the original owner for $175+normal registration fees.
Pending Delete
If the domain is still not renewed by the owner in redemption period then domain name goes into pending delete phase.This lasts for 5 days. After 5 days the domain will be deleted and available to public for registration.
Deleted And Active
The domain name is deleted and available to anyone for registration.