By default, when you specify a Checklist Custom List in the settings, then the checklist form will create a new record in the selected custom list.

However, you can also make checklist forms edit an existing record. To do this, add a field to your checklist with the type "Edit Custom List Record". Other fields in the checklist form must have the same name (at least the same Short Name) as fields used when adding to the custom list.

Once you do this, when opening the checklist form the field that was set to "Edit Custom List Record" will let you select an existing record from the custom list. Upon selecting it, it'll pre-populate all the other fields with the current values. Making modifications to those values will then be reflected in the selected record, to update its values.

This lets you have one checklist that creates a record, and another set of pages that have workflow for updating that record - for example vendor or customer records. 

Note: If you have an approval entry in the article, the changes will only be applied after it has been approved.