Social bookmarking is a centralized online service which allows users to add, annotate, edit, and share bookmarks of web documents.

Many online bookmark management services have launched since 1996; Delicious, founded in 2003, popularized the terms "social bookmarking" and "tagging".

Tagging is a significant feature of social bookmarking systems, allowing users to organize their bookmarks and develop shared vocabularies known as folksonomies.

A backlink for a given web resource is a link from some other website (the referrer) to that web resource (the referent).

A web resource may be (for example) a website, web page, or web directory.

A web search engine is a software system that is designed to search for information on the World Wide Web.

The search results are generally presented in a line of results often referred to as search engine results pages (SERPs).

The information may be a mix of web pages, images, and other types of files.

Some search engines also mine data available in databases or open directories.

Unlike web directories, which are maintained only by human editors, search engines also maintain real-time information by running an algorithm on a web crawler.

Search engine optimization (SEO) is the process of affecting the online visibility of a website or a web page in a web search engine's unpaid results—often referred to as "natural", "organic", or "earned" results.

In general, the earlier (or higher ranked on the search results page), and more frequently a website appears in the search results list, the more visitors it will receive from the search engine's users; these visitors can then be converted into customers.

SEO may target different kinds of search, including image search, video search, academic search, news search, and industry-specific vertical search engines.

SEO differs from local search engine optimization in that the latter is focused on optimizing a business' online presence so that its web pages will be displayed by search engines when a user enters a local search for its products or services.

The former instead is more focused on national or international searches.

Germany, officially the Federal Republic of Germany, is a sovereign state in central-western Europe.

It includes 16 constituent states, covers an area of, and has a largely temperate seasonal climate.

With nearly 83 million inhabitants, Germany is the most populous member state of the European Union.

Germany's capital and largest metropolis is Berlin, while its largest conurbation is the Ruhr, with its main centres of Dortmund and Essen.

The country's other major cities are Hamburg, Munich, Cologne, Frankfurt, Stuttgart, Düsseldorf, Leipzig, Bremen, Dresden, Hannover, and Nuremberg.