interpret results of nvidia-smi
watch is linux command and not related to nvidia-smi command,which using that the nvidia-smi command will be updated every 1 second and it give you a view to see how gpu parameters changing like: RAM usage, temperature, P0(means performance,which p0 is best performance and performance decrease when you get p1,p2,...)

about "can it be used for improving performance of the gpu?" the performance of gpu is showing by p0 so your gpu currently is in max performance.

note that minimum interval for watch command is 0.1 second so if you use watch -n 0.1 nvidia-smi then every 0.1 second the output will be update.

for further information type man watch or man nvidia-smi in terminal.