Questions
What are the notes of standard guitar tuning?
From the thickest string to the thinnest: E2, A2, D3, G3, B3 and E4. In solfège that is Mi, La, Re, Sol, Si, Mi.
What is a cent in tuning?
A cent is one hundredth of a semitone. A string within a few cents of its note sounds in tune to most listeners.
Should I tune to 440 Hz or 432 Hz?
440 Hz for A4 is the standard reference for nearly all modern music. Pick 432 Hz or another value only to match a recording or an instrument tuned that way.
Why does the tuner show the wrong note?
Play one string at a time, let the others stop ringing and stay close to the microphone. A very soft note or a noisy room can make a low string read an octave off.