Proof of Stake (PoS) concept states that a person can mine or validate block transactions according to how many coins he holds. This means that the more coins owned by a miner, the more mining power he has.
A masternode is a full node or a cryptocurrency wallet that is fully synced on the blockchain and is always running 24/7.
In both cases, investors are creating a passive income by holding their coins in the coin wallet or by purchasing and holding a masternode.
In most cases, holding a mastenode is expensive for a single investor and the best way to earn from them is by participating in pools by holding a share of a masternode.