“Sats” (which is shorthand for “satoshis”) is a unit that describes the smallest denomination of Bitcoin that you can send in an on-chain transaction. The unit is named for the pseudonymous creator of Bitcoin, Satoshi Nakamoto. Sats represent 0.00000001 BTC or 1/100,000,000th of a Bitcoin. Much like 1000 meters is equal to 1 kilometer: 100,000,000 sats is equal to 1 Bitcoin.
You are welcome to switch your Swan dashboard units back and forth between Bitcoin and sats, depending on which unit you prefer.