In much of the entertainment industry there is no difference. In my experience these two words tend to be used interchangeably.
However, if you are the kind of person who would like two separate boxes to house these words in, I shall provide them for you!
Dialect is a way of speaking within the same language. So there are various dialects of English. There are various dialects of French, various dialects of Arabic. If you speak Portuguese natively and you’re from Rio de Janeiro, you would have a Rio dialect of Portuguese.
Accent is a way of speaking in a second language which is influenced by your native tongue. So a French speaker conversing in English would have a French accent. An English speaker conversing in Chinese would have an English accent.
Did you like those? very satisfying? Well here are another pair of definitions:
Accent is a change in the way you pronounce words. So you might have a Scottish accent in English, or a French accent in English, or an Indian accent in English. If you pronounce the words in a way specific to some place, whether it's your first language or not, it is an accent.
Dialect is what I might describe as a ‘not-quite-language-yet’. A dialect includes not only different ways of pronouncing things, but a set of vocabulary that is different, and possibly even some small grammatical changes to the language. AAVE (African American Vernacular English) is a dialect and not an accent, for example, because there are different ways of constructing sentences (‘Don’t nobody know what's happening’). Or Scots is a dialect, because it has its own additional vocabulary: calling a woman ‘hen’, or using the word ‘ken’ to mean ‘know’.
Personally, I tend to use the latter two definitions if I differentiate them at all. But as I work in the entertainment industry, I usually go with the flow and use the words interchangeably.