Fretboard with notes
The fretboard is the top part of the neck on a guitar, between the body and the headstock. On the diagram below you can learn all the notes on the guitar fretboard - after the 12th fret it's all repeating again (the 13th fret are the same as the 1st, only one octave higher).
It's good for your development as a guitar player to learn the position of every note. This helps the understanding of chord theory and also makes it easier to play melodies, solos and licks.
It starts with the open strings, when continues with the notes on fret 1 to 12.
The fretboard on the guitar illustrated. After the 12th fret it's all repeating again.
In the fretboard diagram C# (C sharp) is used and not Db (D flat), and so on. If you for example are looking for the note Ab (A flat) this is the same as G# (G sharp).
In the middle of some fret you can find dots. One dot can be found on the third, the fifth, the seventh, the ninth, the fifteen and the seventeenth frets; two dots can be found on the twelfth fret. These have not specific meaning besides making it easier to find the right fret fast.
It is important to learn the notes on the fretboard. If you find it very difficult to learn all you should at least start by learning the tones on the low E and the A strings because the roots of chords are often on these strings.