I often confuse myself trying to keep toffee and caramel straight. In the U.S. toffee is brittle and caramel is sticky. In the U.K., what we call caramel they call toffee. And what we call toffee… that I don’t have an answer for.
At any rate, Chow.com has a nice description of the differences between toffee and caramel, at least in the U.S. sense of the word. As I write this post (Oct. 8), my question on the site (What about what the Brits call toffee?) remains unanswered.