Notes of the Fretboard

Lets take a look at fretboard of the guitar and learn the notes that are on it. First, you will notice that there are six strings on the guitar. Starting with the top string (The thickest string) and going down, the strings are: E,A,D,G,B,E. Or, Eat All Day Get Big Easy. 
The metal vertical strips on the neck are known as the frets. A note is played by pressing your finger in the position between the frets and striking the string with a guitar pick.
Now, lets learn the notes. First, position your guitar neck like this:

 Here is a map of the fretboard with the notes labeled. 

E||-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|---|-E-|-F-|---|-G-|
B||-C-|---|-D-|---|-E-|-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|
G||---|-A-|---|-B-|-C-|---|-D-|---|-E-|-F-|---|-G-|---|-A-|---|
D||---|-E-|-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|---|-E-|-F-|
A||---|-B-|-C-|---|-D-|---|-E-|-F-|---|-G-|---|-A-|---|-B-|-C-|
E||-F-|---|-G-|---|-A-|---|-B-|-C-|---|-D-|---|-E-|-F-|---|-G-|
           III      V      VII      IX         XII          XV

The labeled notes in the above diagram are known as Natural notes. The unlabeled notes are known as sharps(#) and/or flats(b). For example, the note on the E string between the F and G note is known as either an F sharp (F#) or a G flat (Gb). A sharp indicates the Natural notes pitch is raised a semi-tone, a flat note is the natural pitch lowered a semi-tone. 

As you can see, the guitar has 12 notes: A, A#, B, C, C#, D, D#, E, F, F#, G, G#
(Notice that there is no B# (aka Cb) nor is there an E# (or Fb). This is a universal rule in music.)

You will notice that there are many places on the guitar neck to play an A note. Some of these are the same pitch and sound exactly alike. Others may sound different. They are still A notes, but in a different pitch. See the Octaves lessons for a more in depth explanation.  

Also note that on your guitar neck, you probably see round dots on the guitar neck which mark the 3rd, 5th, 7th, 9th, 12th, 15th, 17th frets and so on. These are used as a guide when playing, so you do not need to count frets all the time.

This is your guitar neck and its notes. Get to know it, and try to memorize where the notes are located. This will help you greatly in your guitar playing.