I am just starting to learn GTM, and I feel like this question is a doorway through which I can better understand how one should use GTM.
Previously I've been using GTM to insert GA code to my site, so I am not completely unfamiliar with GTM. But I don't understand what custom image tag does, there are several questions:
1) What is it used for? In Google Help Documents, there is only a small passage regarding custom image tag, https://support.google.com/tagmanager/answer/6107167?hl=en, where 'track' and 'pixel image' are mentioned. I wonder whether custom Image Tag is just used for tracking website data?
2) What are those options for image URL for? Intuitively, I'd think image URL is where you input your
custom image's URL. However, here I can choose "referer","custom event" etc., these are totally different from URL, so what are these for?
3) Once the tag is set, where to see its outcome? For GA code, it is straightforward, you just go to GA page to see the outcome of your Tag. But for this custom image tag, although I've set it up, I don't know where to watch how it works, and the google help doc is not very helpful.