Jelly: A clear fruit substance containing the fruit's juice, sweetened and set with pectin.
Butter: The fruit is forced through a sieve after cooking.
Preserves: A term generally interchangeable with jam.
Marmalade: Jam with the peel, in Britain, it's apparently often bitter.
Confit: Usually means cooking meats in their own fat, and then letting it cool to set, but it can mean cooking fruits in sugar or honey until they're jam-like in consistency.
Conserve: Fruit stewed in sugar.
Curd: Typically, beaten egg yolks, fruit juice, zest, sugar, made into a topping.
Spread: A jam or preserve with no added sugar.
There. I feel so much better, now.