Consensus in a blockchain is basically all parties which are incentivised to be truthful confirming whatever event is being entered making it trustless.
Truth in a central database is not trustless.
Because there is a copy of the ledger on every node and everybody needs to have the same copy. Everybody on the chain (miners, nodes) have it in their best interest to help the network and receive rewards.
In central database truth is controlled by a central authority which is prone to cheating unlike in consensus.
In blockchain everyone needs to agree that information is accurate so it is a collective desicion
in a central system on person can deciede what is true and there is no requirement of verification
In order for a transaction to be added to the blockchain consensus must be reached by the nodes on the network. If the nodes do not reach consensus the transaction is discarded.
In a central database there is a central authority that decides truth. The administrator/s can make changes to the database that may or may not be truthful.
1- Consensus on the blockchain refers to many stake holders coming to an agreement on a particular transaction.
2- A central database has no consensus, information is added without party agreement.
It means that you can see all the interconnections with all the different actors and elements involved, so the anomalies and incoherences will be seen easily and it will make it disadvantageous for anyone to not play by the rules and lie to the system.
In a cenral database, you need to have blind faith that the central actor is telling you the truth, because you donāt have access to all the information about all the interconnections of the transactions.
What does it mean when we say that in blockchain, consensus determine the truth?
How is this different from how truth is determined in a central database?
consensus determine the truth by collectively verifying the transactions.
a central database can decide what truth is and is often not open for everybody. Bitcoins blockchain is open for everybody to se the transactions and you cant get rid of information or change it up.
Blockchain is verified by multiple databases not just one. They must agree on the outcome this is why it is called consensus .
In a central database there is no consensus all the information is controlled by one server. They can change the information by going back to add or delete information.
1 With condenses, it would require having a lot of uninterested parties to coordinate together to make false transactions to be true. However, it would cost an incredible amount of money if in POW protocol. In POS, this means that the bad actors and uninterested parties would be taking money out of their own pocket to give to the bad actors and would cost a lot of money.
2. With a database, the person working the file determines the truth so itās easy to manipulate the outcome vs a group of people.
Technically its considered as a single ledger 
What does it mean when we say that in blockchain, consensus determine the truth?
it means that all parties within the network has been verified an all participants decisions are aligned.
How is this different from how truth is determined in a central database?
in a central data base thereās very lil to no collective effort towards one truth, itsās base on a small group making a decision for the majority which a centralized point of failure.
1- In Blockchain consensus is a party (group of people that work together) deciding something. In Blockchain is really hard to be dishonest because a lot of computers work together to double check information.
2- While in a central database, data is checked and confirmed by a single person that may altered data.
*** What does it mean when we say that in blockchain, consensus determine the truth?**
Duplicate copies of a decentralised ledger of information is distributed across multiple computers and must agree that a new piece of information makes mathematical sense in order for this new information to be admitted onto the blockchain.
*** How is this different from how truth is determined in a central database?**
There isnāt any consensus with regard to the information on a centralised database, and the truth about such information isnāt verified as being true. On a blockchain, all information is trustless but verified.
There needs to be agreement. A number of nodes/people need to agree that something happened for there to be consensus.
In a central database trust is necessary. Not everyone in the network is financially incentivised to tell the truth.
When it is said that in blockchain, consensus determine the truth, we mean that everyone who has had a part of, from inception and origin to, the total history of a certain item or product, is verifying through the chain of a fully connected community involved with said item or product, that the information about to be added to the chain is correct based on an absolute accountability and through incentives.
This is different from how the truth is determined in a central database because a system of trust creates infinite variables with in a supply chain. Meaning that any incentive is now placed with in one governing source or institution. Within this system a supply chain can become inconsistent and subject to manipulation because now the incentive is placed within one governance or control and not with the entire community, in which every single person in the supply chain now has the incentive and is held accountable and thus holding everyone else accountable.
What does it mean when we say that in blockchain, consensus determine the truth?
Consensus eliminates trust. The opportunity for cheating is drastically decreased. The entire blockchain network has the same information to check for verification.
How is this different from how truth is determined in a central database?
A central database may report information without additional verification from other sources. Claims regarding purity or origin of components cannot be validated quickly or easily. The blockchain network ledger achieves truth by tracing details more thoroughly for proof.
What does it mean when we say that in blockchain, consensus determine the truth?
its a consensus of hosts verifying the blockchain all the time
How is this different from how truth is determined in a central database?
It is a distributed ledger, so not relying on any central administration.
Since verify and donāt trust is the motto and verification can only come with consensus it makes blockchain relent on consensus.
Validity on details in a locked database such as central database with no easy or no-public access to provenance can be difficult if not outright impossible. However with consensus based database is only valid because its public and so forth verifiable.