Statuses are disabled by default. They can be enabled on Global Configuration page or individually on a per project basis. The latter option, however, is available only in Issue Checklist Pro.
Statuses are useful if simple checkbox is not enough for your needs.
Statuses available by default are: Open, In Progress, Done and Skipped. You can change that on Statuses page.
When statuses are enabled, checkbox is replaced with a lozenge representing status of the checklist item, as presented on the screenshot below:
A click on a lozenge opens a menu from which a new status can be easily selected:
