Click Stats (for Sellers) (reports >> click stats) is useful when you want to track WHERE your CUSTOMERS are coming from. Tracking is important so that you can pinpoint the sources of traffic that are converting well and bad for you. You keep those that are converting well, and discard those that are converting bad.
If you click on a Funnel, you will see a drop-down list displaying Sub-ID and its corresponding stats. Sub-ID is for more detailed tracking. For example, suppose your Sales Page is:
You can add a Sub-ID on the fly at the end of the url, like:
The Sub-IDs for the example above are:
Note: In addition to adding a Sub-ID for your Sales Page, you can also add a Sub-ID for your Order Button URL.
For example, suppose your Order Button URL is:
You can also add a Sub-ID on the fly at the end of the url, like: