[Bithron]

Nerd:Nerd, as a stereotypical or archetypal designation, refers to somebody who is perceived to be of above-average intelligence and whose interests are not shared by mainstream society. Most people's interests are in the subjects of sports, music, fashion, food, etc., but nerds typically have interests that are more encyclopedic. The term is mostly widely used in the United States, but also has some currency in other English speaking countries such as Canada, Australia, and New Zealand.


Geek:A derogatory term for one with low social skills, regardless of intelligence. Similar to common use of the word dork. (Late 20th century.)
OR
A person who has chosen concentration rather than conformity; one who pursues skill (especially technical skill) and imagination, not mainstream social acceptance. Geeks usually have a strong case of neophilia. Most geeks are adept with computers and treat hacker as a term of respect, but not all are hackers themselves - and some who are in fact hackers normally call themselves geeks anyway, because they (quite properly) regard 'hacker' as a label that should be bestowed by others rather than self-assumed.


From:Wikipedia