“Sats” (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. You can do toggle back and forth on the top of your dashboard: