In privacy,
only your friend or some one who have your blogger address can see the content in the blogger
In twitter, everyone who surf on the twitter website can see your tweet and put some reply for you
:up: Twitter calls itself 'microblogging'. The limit is 140 characters (not words). Many people use it as a sort of index to blogs - a typical tweet might be 'Just blogged about X: http://tinyurl-etc' or 'Seen N's latest blog? - brilliant: <link>'
Afterthought: don't let the 'er' spelling fool you. Twitter is a site (and the site was named after what little birds do: sparrows were twittering centuries before the WWW came along ;-)). A blogger is a person.