A site scraper is a type of software used to copy content from a website.
Site scrapers work similarly to web crawlers, which essentially perform the same function for the purposes of indexing websites. Web crawlers cover the whole Web, however, unlike site scrapers, which target user-specified websites.
Depending on the particular scraper program and user specifications, the software can download any data, including entire websites, and follow links to other content for further downloads. The data obtained may be saved as text, CSV, HTML or XML files; some scraper tools also enable export to a compatible database.
Examples of site scrapers include Web Content Extractor, Wget, ScrapeGoat and Scraper, a Chrome extension.
Asheesh Laroia explains web scraping in this video: