Duplication / content theft. Content is duplicated when 2 or more pages intentionally or accidentally contain the same information. For search “spiders”, each unique URL, which they can find is a single site page, even if different addresses refers to the same document. Search engine robots usually find new addresses for the links on the pages, which they already know.
Links can be both internal (within the site) and external, i.e. from another resource. Webmasters often create different URL-addresses that lead to the same document.
Usually, this is not intentional, but the problem of content duplication occurs in any case. Duplicated content are especially spread in large, dynamic web-sites, but small sites are often faced with it as well.
The most popular websites platform is WordPress. Unfortunately, if you do not carry out fine-tuning of WordPress, and use the default settings, then you’ll definitely have some amount of duplicated content. You’ll meet problems with headings, tags, archives and some others.
Site owner knows about how much articles and offer columns are on the site. The owner of an online store knows how many products are in the assortment, how many categories were created and informative articles posted. The number of pages on the site should be approximately equal to the sum of these values.