Public blockchains are decentralized and distributed across a large network of computers (at least that’s its intention). This reduces the opportunity for data tampering, which is designed to create trust in the system.
Some blockchains can be public and open to anyone. Others can be private. There are also hybrids which can use variations of public and private data.
One profound factor of blockchain is the bypassing of a reliance on third parties, such as lawyers in the real estate and other markets, to verify the actuality of certain circumstances — land titles, for example. The video above explains blockchain and its capacity to reduce the need for intermediaries.