There is also a distribution pos. I’m not 100% how it works.
It’s like x nodes are elected to build the blocks and thus receive the among award.
To be eligible for election you need an large amount of that coin, aka proof of stake.
People that aren’t elected can use the coins there hold as vote. Not sure how that is.
The leading style of PoS that originates from Peercoin has some issues, mainly vulnerability to certain types of attacks and propensity to fork. Because of this, it is usual for developers to publish checkpoints periodically and this is a form of centralization, because the chain with most weight is supposed to emerge from network consensus and not from a “royal decree”.
There are other styles of PoS, such as the one in Nxt, where everyone knows who will be eligible to mint the next block (whereas in ppc it is a lottery), and systems like “delegated PoS”, but I don’t know how they actually work. AFAIK they are not entirely free from centralization pressures either.
In my opinion a true decentralized proof-of-stake would be the holy grail of crypto. All forms of proof-of-work tend slowly but surely to miner centralization (and huge consumption of energy). There are some individuals who think that a decentralized cryptocurrency is a pipe dream, but let’s hope that is not the case.