Each Pricing Package that you create on FINANCE >> MEMBERSHIP PLANS is going to generate an ID on the system. This ID is used to recognize that particular package on different areas on the backend of your website. This number represents a Membership Level on the database.
You will see this ID being used on the Pricing Menu. These ID can be used also to moderate what membership levels are allowed to showcase on various streaming widgets on the Homapage, please see the following article: (Bootstrap) How To Add Content On Your Homepage (Coupons, Newest Members, Main Categories, etc)