In the Blockchain, all transactions are publicly announced to all nodes, as there is no central authority who validate transactions. The validation system is called Proof of Work.
This paragraph is somewhat misleading. The POW isn't used for validation, it's there to prevent double spending and modification of the chain. Validation of transactions in the block is done via cryptographic signatures and has nothing to do with POW. I would emphasize this more, as it's abit unclear from your post what is the purpose of POW in Bitcoin.
Yeah, I just learned about that reading some posts on some other threads. I will review this text soon. Thank you for your observation.
Can you explain about 6 confirmations needed for a transaction to be finalized?
It doesn't need 6 confirmations to be finalized.
Bust many exchanges and websites will wait for 6 confirmations before accepting it, as a transaction is only considered irreversible with 6 confirmations.