Martin Fowler has a page on UI design patterns, in which he defines and then talks about MVC, MVP and other patterns.
http://martinfowler.com/eaaDev/uiArchs.html
To summarise the differences, Controllers in the MVC have more control over the UI, and handle events, while a presenter in the MVP is more passive, and just presents information through the UI.
In general there's not much difference, and often the line between them is blurry.
