What is "who's who"

alt. 1 (context uncountable capitalized English) A publication containing biography of well-known or important people. 2 (context uncountable English) A list of notable, famous, or upper-class people. 3 (context uncountable English) Collectively, the elite class. 4 (context countable English) A person appearing in a http://en.wikipedia.org/wiki/Who's%20Who publication. 5 (context countable English) A celebrity or famous person, someone likely to be in such a publication. 6 (context uncountable idiomatic English) The identity of specific people, understood in terms of such distinguishing characteristics as their backgrounds, prominence, achievements, jobs, etc., as a basis for compare them and especially as a basis for ranking them within a social group. n. 1 (context uncountable capitalized English) A publication containing biography of well-known or important people. 2 (context uncountable English) A list of notable, famous, or upper-class people. 3 (context uncountable English) Collectively, the elite class. 4 (context countable English) A person appearing in a http://en.wikipedia.org/wiki/Who's%20Who publication. 5 (context countable English) A celebrity or famous person, someone likely to be in such a publication. 6 (context uncountable idiomatic English) The identity of specific people, understood in terms of such distinguishing characteristics as their backgrounds, prominence, achievements, jobs, etc., as a basis for compare them and especially as a basis for ranking them within a social group.

Who's Who'' (or "Who is Who''") is the title of a number of reference publications, generally containing concise biographical information on a particular group of people. The title is also used as an expression meaning a collection or group of noted persons; as in the sentence, "The actors in the film were a Who's Who of the great American comedians of the time".

The title "Who's Who" is in the public domain, and thousands of Who's Who compilations of varying scope and quality have been published by various authors and publishers. The oldest and best known is the annual British publication Who's Who, a reference work on contemporary prominent people.

Many publications using the title are vanity publications, where the inclusion criterion is the biographee's willingness to buy the book, with the business model consisting of selling books directly to the biographees.

Who's Who is a leading source of biographical data on more than 33,000 influential people from around the world. Published annually since 1849, and as of 2015 in its 168th edition, it lists people who influence British life, according to its editors. Entries include judges, civil servants, politicians and notable figures from academia, sport and the arts.

Each entry in Who's Who is authored by the subject who is invited by the editors to fill in a questionnaire. Entries typically include full names, dates of birth, career details, club memberships, education, professional qualifications, publications, recreations and contact details.