A stretch goal is an extension of your target, where you specify the extra funds required to get your art to the next level.

Remember, not everyone you ask to give will give, so even a modest crowdfunding campaign aiming to raise a few thousand dollars requires getting in front of thousands of people.
Unless you’re famous in your own right or have strong social influence, it’s unlikely you’ve got immediate access to a network of this size. Here’s where PR comes to the party.