What's a callout?
It's a simple graphic, used to hold some text, such as a dialog for a cartoon character, or some verbalized sound effects (POW!, OUCH!, SLAM!)

Example:
Project Dogwaffle 11 includes a collection of callouts, to help you with creating illustrations with annotations.
There are over 150 presets and you can easily make more.
It makes it easier to depict a dialog too, for all you cartoonists and 2D/3D illustration artists.
Here are more examples:
More samples and free giveaways for users outside of Dogwaffle 11:
updated! more callouts and tutorials
see how to make more custom callouts with Affinity Designer and other tools!