[pgwhalen]

This is mostly correct except for the last sentence, for any conventional definition of "clearer." You could replace "clearer" with "market maker" to be more correct, but it is important to note that the market maker isn't earning the spread every time they trade with you. They're only earning the spread in the aggregate, which is to say that they hope to both buy and sell with many people like you so that over time they are effectively earning the spread.