Fuck yeah
Appearance
Fuck yeah is a growingly popular interjection with (particularly young female) people in the United States. The term denotes enthusiastic approbation and also is commonly voiced by young porn starlets engaging in vigourous sexual activities.
Mechanics
Outside of its use during sex, an exchange where the term is appropriately employed can be something like this:
Person #1 : "So, do you want to go to Boston with me next weekend?"
Person #3: Fuck yeah!
Synonyms
Fuck yeah is similiar to hell yeah, albeit more intense and profane.
Fuck yeah around the world
The use of the term originates in the United States but is growing in Great Britain, mostly in Scotland, which has closer ties to the US than England. Usage of this term is veritably non-existant in France and Germany, however.