This is a good article:
https://bpdfamily.com/content/codependency-codependent-relationshipsIn a codependent relationship, there is one person with dysfunctional habits (addiction, poor mental health, immaturity, irresponsibility, or under-achievement) and a person who enables them. Enabler and enabled. Bottom dog, top dog.
"Supply" and "Prey" are Internet lore or metaphors used that are used in place of the basic codependent dynamic of enabler and enabled.
Supply and user or
prey and predator. The difference here is that one party doesn't have a role - they are an innocent victim.
Given all the emotional wounds that ultimately come from a codependent relationship, it is often easier to think of things in terms or victim (innocent) and victimizer than to accept that we had a very active role in creating and sustaining the heartbreaking relationship we were in - that there are a lot of self inflicted wounds.
Most members grasp the "codependent dynamic" later in the healing process. It's important to grasp this concept so that we do not repeat the experience again.