Can someone explain what latency is inbf1

Latency essentially is the time it takes for your computer to send data to the server you're playing on combined with the time it takes for you to receive data back, the lower your latency meaning the less time it takes and the higher your latency the longer it takes. In Battlefield 1 having a lower latency is preferably since it means you'll be more in sync with the server so to say, this is much easier to achieve in servers closer to where you live or in your region, such as East Coast or West Coast American servers for example.

This is measured by ping in-game which'll be the number next to yours, and other players names in the scoreboard. Similarly servers in the browser should mention what ping you should be getting if you tried to connect.