For some sort of clarity let me outline some of the different types of blockchain/decentralised ledger technology systems and the business case for them.
Open or closed would describe who can view (or read) the data. An open system would show all the data to anyone, a closed system would restrict who can see this data.
Public or private would determine who can write (or create) data. For public this would be anyone, private systems would add restrictions.
So an open and public systems tend to be used for cryptocurrencies that offer a store of value (bitcoin), payment services (ripple), or programmable networks (ethereum/de-fi). Data is identified by using a public address but owned by the person who holds the private key.
A closed and private network like Corda [and Hyperledger Fabric] would require some sort of identity access management. Typically participants only share a subset of their data with relevant customers as it may be commercially sensitive (Alice may not want Oscar to know that Bob pays less for a widget). Trade finance, supply chain, or any system which would benefit from "trusted" shared data would be the typical use case.
An open and private system would suit the publication of laws, publicly viewable tax returns, public announcements, and similar. Closed and public would suit voting use cases.
...and then there are central bank digital currencies (CBDC) - but that's a whole new topic!
Hope this helps a bit, for a nontechnical introduction I'll recommend the free Enterprise Blockchains Fundamentals
course from 101 Blockchains.