What is an Index?
The Internet contains billions of web pages and other resources, but if you don’t know what’s out there or where it is – what can you do?
You go to an Index.
An Internet Index is a collection of things on the Internet. You can search through it and it will tell you where those things are.
It can contain exact copies of web pages, or just a few lines from the top. Or, it might just have a bit of pre-digested or ‘meta’ information like a simple description or a few keywords.
In its basic format, an Index is just a file on a computer. In more complicated variations it can become a bunch of files on a bunch of computers.
An Index is a collection of addresses and information about the things to be found there. In an extreme example, it can contain copies of the things itself, or it can contain portions, or just some pre-digested bits. It provides a fast way to get at information in an orderly way. It is a list of items with a description, linked to an address.
An Index isn’t the same as a search engine, but the two go together, so it happens that people mix the terms.
You use a search engine to look in the Index for things you are interested in.
When you do a search, the search engine program reads through the data collected in the index, looking for things that seem to fit your request.
It returns with results for you to look at, and most importantly, knows where it found it. When you chose something, it can take you there.
The better the search engine is, the better it will be at letting to specify your interests, interpreting what you want, and filtering though the Index looking for the right matches.
The Index is built and continuously maintained by software written to poke through the Internet looking for ‘stuff’. These ‘spiders’ or ‘robots’ collect web pages and follow links, and information flows through them into the Index.
Resources on the Internet – web pages, documents, images, files, music, video, etc – are contributed by all sorts of people and groups throughout the world, and generally are made available to the public. The Internet is a vast library of materials made available by the public, for the public.
Anyone can contribute material to the Internet, and consequently all kinds of things are waiting to be found – if you only know where to look.
To do that, you have to rely on the many indexes, catalogues, and directories that have been created and made available for searching by their owners.
There are no indexes which cover all of the Internet and none are able to keep up with the rate of change.