You can check the guidelines for a specific tag in the tag page, e.g. dev.to/t/help. The tag labels are also links to the tag page.
Regarding the tags that have special behaviour, I don't know of any page explaining it, but basically a post tagged with a tag that appears in the sidebar may appear in the sidebar and has the tag highlighted in the feed.
You can check the guidelines for a specific tag in the tag page, e.g. dev.to/t/help. The tag labels are also links to the tag page.
Regarding the tags that have special behaviour, I don't know of any page explaining it, but basically a post tagged with a tag that appears in the sidebar may appear in the sidebar and has the tag highlighted in the feed.
oh, I saw those but it never occurred to me to re-read them. They're do state a pretty clear intention for the hashtag. Thanks!