What is the purpose of a ref?

Could you please elaborate on the purpose of a "ref" in the context of cryptocurrency and finance? Is it a reference to a referral program, a reference number for a transaction, or something else entirely? Understanding the specific use case would help me provide a more accurate and detailed answer to your question. Additionally, could you please clarify if you're referring to a particular platform or system where "refs" are used, as the purpose may vary depending on the specific application?