What is permissioned and permissionless blockchain ?

[arnav029]

So as a beginner and exploring different elements of blockchain , I came across this term as permissioned and permissionless blockchain.
And I started wondering about the applications of these. I read the bookish definition of both , but the fundaments aren't yet clear to me.
So can someone please explain me these terms? And also which of them is used by cryptos.

[othaime-en]

Hey @arnav029 permissionless blockchain is the normal public blockchain like blockchain and ethereum where no one controls anything, it is the public that dictates everything about the network. Entry and exit are free, there are no restriction as to what you can access in the network. Everything that is on the network is available for everyone to see, No priviledges involved. This is the main concept that you hear about when people talk about blockchains.
Permissioned blockchain on the other hand, has some form of centralization in the network whereby someone has some form of control on the level of access and actions a user can do in the network. This form of blockchain is mostly available in the corporate sector where the organization doesn't want all the data to be accessible to the public, just some part of it. A permissioned blockchain is normally partly accessible to the public and in most cases, the organization controls who gets to enter the network and what data they get to see. A good example of a permissioned blockchain would be a supply chain application on a blockchain whereby only the suppliers can join and they get to see the product lifecycle from production until it reaches them. This is just a simple explanation. Feel free to ask for more information if you still don't understand.

[arnav029]

So yeah , I got the concept of permissioned blockchain , which was I guess a different concept than usual.
But the main question in general I would like to ask is , why was need of creating such blockchain which is centralised or kind of controlled by an entity .
Could have just created a website lol.

[krakxn]

So yeah , I got the concept of permissioned blockchain , which was I guess a different concept than usual. But the main question in general I would like to ask is , why was need of creating such blockchain which is centralised or kind of controlled by an entity . Could have just created a website lol.

The reason being that permission-less protocols are very slow relative to the permissioned ones.

[krakxn]

The only difference between permissioned and permissionless blockchains are the set of validators and the users w/ access to arbitrary changes to parameterization; everything else is identical.

In permissioned systems, there is a constant (permissioned for addition) set of validators; in permissionless systems, there can be arbitrarily any sets of validators.

From the above, it follows that in a permissioned system, the ledger is not publicly accessible because the validators are pre-defined by the user w/ access. Similarly, in a permissionless system, it will be public because the validators are not pre-defined, rather, they can arbitrarily take part in the consensus or not--thereby making it public. Additionally, the TPS for the former will be higher than the latter as the communication b/w nodes is easier for a centralized set of validators than an untrusted system where nodes have to verify every message. It also follows that the former is more centralized than the latter. However, the latter isn't so better as well-->50% of Bitcoin's (similarly for Ethereum, despite the Merge) hash rate is dominated by just two mining pools. Not so decentralized is it? Just a facade for retail.