Server Performance – The effectiveness of a server, including throughput, individual response time, and availability – if you have that symbol that means the server you’re playing on is crapping itself and everyone playing on the server should lag and see the same symbol
Packet Loss – is the failure of one or more transmitted data (like your ingame location, your shots, your current ammunition count, the animation youre doing right now) to arrive at their destination (the server) to be “distributed” to all the players – if you have that symbol check your internet connection because you will lag pretty badly
High Latency – is an expression of how much time it takes for a packet of data to get from one designated point (your pc) to another (the server) – if you have that symbol it means your internet connection is crapping itself depending on how high the ping is (usually anything above 100-150 is bad for battlefield)
Latency Variation – if your pc and the server have a too big ping difference this symbol shows up, mostly comes along with the High Latency symbol
Low FPS – something wrong with your game, can be fixed in most cases with updating to latest drivers on bf1 unless you have a bad pc
Refresh rate – the number of frames per second your monitor can display (60hz etc.) – no clue what it means in battlefield as I never saw it.