You send: Dai (Arbitrum One)
Dai is a dollar-pegged stablecoin issued by the Maker protocol and backed by on-chain collateral rather than by a company holding reserves. It is an ERC20 token, so sending it costs Ethereum gas. More about Dai.
On this pair it moves over Arbitrum — an address there starts with 0x — 42 characters.
DAI also exists on other networks — different addresses, not interchangeable: BEP20, ERC20, Optimism, Polygon.

