Here is. more or less, what my canning sources have to say about the distinctions between the assorted fruit spreads (in the US, anyway):
Jelly is the jelled juice of a fruit (or something like wine). Generally, jelly contains no pieces of fruit, although specialty jellies, like pepper jelly, may include pieces of jalapeno or other pepper.
Jam is made from crushed or chopped fruit. Jam often has a soft pulp, but it does not contain chunks of fruit.
Preserves are fruit chunks suspended in a jelly base.
Marmalade is a soft jelly, often citrus-based, that includes both the peel of the fruit suspended throughout the jelly base.
Conserve is a mixture of more than one fruit, often with added nuts and raisins.
Fruit butter, such as apple butter or prune butter, is fruit puree or pulp combined with sugar, lemon juice and spices. It usually does not contain any added pectin-rather it is cooked down to its final consistency. It doesn't actually contain any butter.