Glossary
Click ID
A unique code assigned to a single click, which travels with the visitor through the funnel and comes back with the conversion. Your tracker issues one, and ad platforms add their own: gclid from Google Ads, fbclid from Meta.
Also called: click_id, clickid, transaction ID.
The tracker creates the ID on the click and writes it into the offer link, usually into a sub parameter. When the network records a lead, its postback returns the ID, and the tracker matches the conversion to the source, creative and placement. Names vary: Binom uses the {clickid} token, while Keitaro's click ID is {subid}, which confuses anyone who also works with sub IDs.
Platform IDs work in the opposite direction. Google Ads auto-tagging appends gclid to the landing page URL, and offline conversion import sends sales back to Google keyed to it; Meta adds fbclid to links clicked on Facebook. The common failure is a redirect or a form that drops the query string, so the ID never reaches the page that needs it. Google's help warns that redirects must pass gclid through; a test click shows whether yours do.
Related terms: Sub ID, Postback, Tracker, Tracking link, UTM parameters.