Social search refers to Internet search services that use social networks or relationships between people as a key factor in how they order the results of search queries.
The social search concept took off a year or two after Facebook popularized online social networking. A bunch of startups launched Web search services that ranked results based on what people were searching or clicking on within a particular circle of people--user of a specific website, for example, or a social network like Facebook.
Social bookmarking is another example of social search, since it offers a mechanism for people to share their favorite Web links and see what's most popular within a social group. Another Web concept related to social search is social ranking, in which people actively rate material online, and those rankings influence the presentation order for content that other people see.
Other names: Social search engine basically refers to the same thing as social search.
But both "social search" and "social search engine" refer to something slightly different from "social networking search services."
Social Networking Search is Different
Social networking search services enable you to search for material posted to social networks; they don't look across the entire web and order results based on social relationships, like social search engines do.
SocialMention is an example of a social networking search engine; it's designed to index material from a wide variety of social media sites.
Google Social Search
Google, the giant of Web search, developed its own flavor of social search in late 2009 and has been evolving it ever since. In its earliest stage, Google social search primarily indexed content on social networks like Twitter and Facebook and surfaced that material in specially highlighted ways when people ran Web searches. Next, Google integrated that material more seamlessly into its regular search results, but it still wasn't analyzing social relationships to determine the relevance of other Web material.
Google social search has continued to change a lot. In January 2012 the company rolled out a controversial revamping of its Web search service which it called "Search Plus Your World."
The new Google social search shows more personalized results, such as private information the person doing the searching has shared on Google+, as well social networking profiles of people they know.
