From probably most common to least common: Pronunciation (how words sound) Slang / Vocabulary (different words used to express the same idea) Spelling Meaning (the same words are used to express different ideas) about.com has a great article on some more differences here: http://esl.about.com/od/toeflieltscambridge/a/dif_ambrit.htm

The following site has a person say aloud the words or sentence that you have typed in. Choose the accent after you type in your word/sentence and you will hear the difference. http://www.oddcast.com/home/demos/tts/tts_example.php?sitepal

Well, there's the pronunciation, spelling, vocabulary, grammar, and so forth. But we can still understand each other, more or less.

Hi dear friend American English and British English are diffrent in pronounciation and in some vocabulary, They also differ in spelling but in a very small amount of words. But the most significant difference is the pronounciation. :)