The @callback tag provides information about a callback function that can be passed to other functions, including the callback's parameters and return value. You can include any of the tags that you can provide for a @method.
Once you define a callback, you can use it in the same way as a custom type defined with the @typedef tag. In particular, you can use the callback's name as a type name. This allows you to indicate that a function parameter should contain a certain type of callback.
If you want a callback to be displayed with the type definitions for a specific class, you can give the callback a namepath indicating that it is an inner function of that class. You can also define a global callback type that is referenced from multiple classes.