What is the difference between butterscotch, caramel, and toffee?
Butterscotch and caramel are very different things. The taste difference between the two is far from 'slight' in my opinion.

Caramel is typically made with granulated sugar, milk and/or cream, butter, and sometimes vanilla. The primary flavors of caramel are the sugar and milk/cream.

Butterscotch on the other hand is made with brown sugar. It's primary flavors are brown sugar and butter. It typically also contains milk/cream but they are not as prominent as caramel.

Toffee is butterscotch that has been cooked to the hard-crack stage.

There is no liquor in butterscotch.

There is a lot of leeway in what things get called caramel, butterscotch, and toffee. The important differences to keep in mind are that caramel is made with granulated sugar, whereas toffee and butterscotch are made with brown sugar and much more butter.