Is PBFT a consensus algorithm? Can we consider PBFT (Practical Byzantine Fault Tolerance) as a consensus algorithm ?

And if yes, How does it work?

And is it similar to other consensuses such as PoW, PoS or PoA ? Or it is totally different?

And is it used actually in a blockchain platform? if yes, which one?

P.S. I heard that it is NOT scalable for large network, Is it true? And if so, is its scalability even worse than PoW?
PBFT is Practical Byzantine Fault Tolerance. It is a "classical" consensus algorithm that uses a state machine. Uses leader and block election to select a leader.

PBFT is a three-phase, network-intensive algorithm (n^2 messages), so is not scalable to large networks