What is spider or crawler and how its perform?

Crawler is a software who search out the almost all relevant data from directory server.

A web crawler is a relatively uncomplicated automated system, or script, that methodically reads or “crawls” through Internet sites to make an index of the data it’s looking for.Alternative names for a web crawler incorporate web spider, web automatic robot, bot, crawler, as well as automatic indexer……………………….

Crawler, spider and trading program all tend to be same, gather facts from any site exactly like content, hyperlink and alt label and retailer in catalog server.

A spider or crawler is really a relatively uncomplicated computer program which comes after certain links on the net & gathers information the way it goes.