&gt;blockchain aims to solve the &quot;Two Generals&#x27; Problem&quot;[0] short explanation in video[1]<p>PoW aims to solve that.  Blockchains are just a way to store data in an agreed format with immutability and known ordering.<p>&gt;On what the article says, transactions not relying on the first bitcoin blockchain are more vulnerable to 51% attacks<p>51% attacks are an issue for PoW systems.  Private chains don&#x27;t need PoW so aren&#x27;t vulnerable to them.