The referrer header is the default way of tracking referrer sources of web traffic. It works well for the majority of cases but not every request from a browser will have the referrer specified.
You may be familiar with the (direct)/(none) referrer source in the Google Analytics or the term “dark traffic”. This basically covers all the traffic where the referrer is not passed. These could be clicks from email, from messengers such as Telegram and more.
To track these sources you could add a special query parameter to your link before you post it for instance Telegram. See here on how to do that.