im about 5'9 with a 54 road bike frame that im converting into fixed gear

shopping for new crankset right now and had a few questions

im lookin for 48t chainring
whats difference between 1/8 and 3/32 chain?

alot of them say like 130 BCD - wut is this?

and they also say like 160 or 165 mm too - what measurement is this for?