butterfat = fat from dairy butter
cocoa butter = not from dairy butter, from cocoa (which is a bean) with a buttery texture (bit like peanutbutter)
eta: i think if something says 'something'-butter, or butter-'something', and you can't identify the other part as being non dairy, its safer to give it a miss. non dairy -butter things could be shea, cocoa, peanut, cashew, maple, apple (careful of this one, cos it could be a really concentrated fruit puree, or it could be butter with apple stirred into it), etc... beans, fruit or nuts.
another one to watch for (though not likely in chocolate) would be ghee- another sort of butter oil, otherwise known as 'clarified butter'. might turn up in indian sweets, desserts and chocolates.