You send: Chainlink
Chainlink is the oracle network that feeds outside data — prices above all — into smart contracts, and LINK is the ERC20 token that pays its node operators. It lives on Ethereum, with bridged versions on other networks. More about Chainlink.
On this pair it moves over ERC20 — an address there starts with 0x — 42 characters.
LINK also exists on other networks — different addresses, not interchangeable: Arbitrum, BEP20, Polygon.