LINK is the name of the proprietary token and it is used to give the oracle (validator nodes) in the network a reward for their work. Please note that you do not have to participate in the network and become an oracle to invest in LINK. Anyone can buy and sell LINK, which is built on one of Ethereum's token standards, ERC-20. LINK has a limited supply of one billion and was distributed via an ICO in 2017.