Butterscotch is a confection (like candy) made from brown sugar, butter and cream. It is a bit like toffee but is made differently. Butterscotch is made by boiling sugar until it is at the "soft crack" stage, which is a slightly lower temperature than for toffee. Butterscotch can be used as a sauce for desserts like ice cream.
Butterscotch Sauce at Wikibook Cookbooks