What is the difference between sentiment analysis (e.g. on Facebook) and Twitter sentiment analysis? I'm bit confused with the names of sentiment-analysis and twitter-sentiment-analysis.I want to do sentiment analysis for facebook fan page posts.so I decide to use an api but I did not found any api which gives sentiment analysis for facebook Posts.Every api service is made twitter.I found datumbox api which gives results for sentiment-analysis and twitter-sentiment analysis here.

for facebook sentiment analysis, do I need to go with sentiment-analysis api or twitter sentiment-analysis.(I know Name itself suggests sentiment is for twitter tweets).

Is their any api that provides sentiment analysis for facebook posts data ?

or 

facebook trained datasets with the classes of POS,Neg,Neu?
There is nothing specifically called Twitter sentiment analysis, rather its colloquial. Sentiment analysis is a common term and could be applied on any dataset depending upon the use-case considered.

I have not came across any facebook api for scraping posts (maybe there are privacy concerns, as sometimes you cannot see fb pages when you are not an user), nevertheless there are several apis to scrap tweets from twitter, even specifying person, geographic location, language.

here is a github gist for reference, it uses python tweepy module to grab current tweets.