ISP's - Internet Service Providers e.g. Telstra, Optus, IINet, IPrimus, TPG, etc. The ISP's then allocate individual addresses, e.g. 202.139.83.152, to each computer, or computer network, as required.

Note that within the APNIC membership, there are also five National Internet Registries (NIRs), in Japan, China, Taiwan, Korea, and Indonesia.

The WebMetrix network keeps AusRegistry updated with any changes to this IP address.

Your ISP caches (remembers) that name and IP address for, say, 48 hours, then deletes the record automatically. The cache reduces Internet traffic, and the automatic deletion (which means that the next time the name is requested, the ISP has to look it up again), enables a domain to change server hosts with only a 48 hour time delay for most ISP's to be updated.

Your PC saves a copy of the actual page in its cache, downloading a fresh copy normally only when the file size, or time of last update changes.

Google and other Search Engines store words and phrases, associating them with unique domain / page names.

They do this by simply following the hyperlinks within the web pages they know about, thus discovering new ones, and are thus building and refreshing the information in their databases continually.

Also, thus, when they display a search result, it may be a somewhat "stale" copy of the page. When you click on the link to download it, you then see the latest copy.