customer-accounts Customer Accounts / Profiles

Can someone break down for me the class distinctions between Customers, Subscribers, Members, Donors and Leads? I feel like I need a venn diagram to picture which of these titles cross reference and which ones don't. For example, I am under the impression all Members are also Customers, but all Customers are not necessarily Members. 

I need a clearer understanding of what actions create each type of account to understand which lists cross reference. Thank you.