Copywriting is writing with a job to do
It is the writing with a practical purpose. Usually, that purpose is to make the reader think, feel or act differently from the way they did before.
Most copy is written to sell products or services, so crossing the bridge means buying or trying something. But you could also be aiming to provide information, explain ideas or build support for a cause. If so, you’re trying to get the reader to buy in rather than buy – to invest their attention or commitment instead of their cash.
Either way, you have to respect your reader, give them something interesting and always remember that they’re human.