TTL

From JumbaWiki

TTL (time to live) is a limit on the period of time that a piece of information is kept before it should be discarded.

In the Domain Name System (DNS) the TTL is set by an authoritative nameserver for a particular Resource Record. When another nameserver queries the authoritative nameserver for a Resource Record, it will cache that record for the time (in seconds) specified by the TTL. If someone queries the caching nameserver for the same record before the TTL has expired, the caching server will simply reply with the already cached resource record rather than retrieve it from the authoritative nameserver again.

Shorter TTLs can cause heavier loads on an authoritative nameserver, but can be useful when changing the address of critical services like web servers or MX records, and therefore are often lowered by the DNS administrator prior to a service being moved, in order to minimize disruptions.

Hosting resellers can change the TTL for their domain using Zone Manager in Web Host Manager.