If you want to define different entry points into the bot for your users or track which campaign your users found in your Facebook bot through, you can use the so-called Ref Id from Facebook (assuming Facebook is used as a channel). Ref in this case stands for referral and means that you can forward a self-chosen value to the bot. You can set this value to any value you like.
How to build the appropriate messenger link for this, you can read here.
When the link is called, the bot is started and the RefId is automatically read by the bot and can be used in the user context. How you can use context parameters in your bot, you can find here.