In simple terms, think of a Blockchain as a Spreadsheet. A BIG Spreadsheet. When someone wants to record some information and enters it on the Spreadsheet, the information is then verified and shared on the network. The Spreadsheet is then copied and distributed. If you want to change the information, the original entry can NEVER be deleted. It can be changed, but NEVER deleted. You have to create a new entry and repeat the verification and distribution again. Hope this helps. Stephen