What is the difference between a public and a private blockchain?

A public blockchain is an open and decentralized network that requires no permission to join or access and is visible to anyone on the internet. This type of blockchain allows anyone to view, contribute to, and validate transactions. A private blockchain is a closed, more centralized network that requires authorized entry before being able to view, contribute, and validate any transactions. This type of blockchain allows for more control over who has access, which in turn gives companies more security and control over the network.