Commercial is an adjective describing something with money-making and marketing intentions. If you’re a bit of a book snob, steer clear of commercial fiction, which is written for the widest enjoyment.
The adjective commercial first appeared in the 1680’s, long before television commercials, which is probably what you think of when you hear the word. An al was added to commerce, and it meant "pertaining to trade." It wasn’t until the 1870's that commercial meant “done for the sake of financial profit,” and then later in the 1930's, the noun form was refined to describe “an advertisement broadcast on radio or TV.”