A reporter allows any module to display additional information e.g. on a click event. You can only define and customize one reporter in i3-status. All modules will use the same reporter.
Example output of the i3-status-travis module, showing a list of projects and their build status.
Currently only one reporter is available. The i3-status-reporter-html displays the content in a popup window using html.
You define the kind of reporter you want to use in the config YAML file.
main:
[...]
reporter:
module: i3-status-reporter-html
All additional configuration or customization options are based on the reporter itself. The documentation of the reporter should contain all information you need to configure your reporter.
If you want to implement your own reporter please have a look at the noReporter class.