Accent and dialect
Accent and dialect are two words with similar meanings - which should not be confused in academic English. In the context of language, each describes an aspect of the way language is produced. It is most usually a question of where the speaker comes from, though social class and education can also be influential.
accent refers purely to the way a speaker sounds - essentially the vowel sounds. Any native Briton can tell that a speaker comes from the USA; Americans can often be more precise - "he's from Texas", "she's mid-western" etc. Equally, in Britain we can tell which part of the country an interlocutor comes from; and an English person, for example can usually tell that someone is Scots. (A Scotsman may be able to tell which part of Scotland.) For a brief account of the most important accent in the UK, as far as formal English is concerned, see Received Pronunciation.
In contrast to accent, dialect in language is about more than sound. It means the particular sub-set of a language used by a particular group of people in terms of vocabulary, idiom and grammar as well as sound. It is possible to read any English text in any given accent with the words as written; it is not possible to perform a given text in any dialect other that that in which it was originally written. For a brief account of the most important dialect for academic writing, see Standard English.