Ph Meter?

Hello Guys,
I have just bought a pH meter which comes with an extra ph4 and ph6 buffer soloution? and i am really unsure on how this all works, what do these do or change? do i also need a caliburation fluid? what is that?
if anyone please can help.
thankyou very much.

the buffer solution is the calibration fluid. put the sensor in the solution and adjust as needed. say you use the ph4 and your meter reads 4.6, adjust the set screw until your meter reads 4.0. hope this helps

What is the make and model # of your tester?