What is this symbol?

“Fee rate: 10 sat/vB”
It seems to be saying 10 sat per vB. What is vB?

vB = virtual bytes

10 sat per vB means that the miner allocated for the transaction will be 10 sats per virtual bytes.

The minimum sats per vB Bisq uses for trades is 10 sats/vB this is to ensure trades confirm and pay out with an adequate fee.