Guitar Tablature:

Tablature (tabs) is often used by musicians who play fretted stringed instruments (e.g. guitar and bass) most guitarists prefer tabs over musical notation as it provides an easy to read way of writing music specifically written for fretted instruments.

What are frets?: The long neck of the guitar is made up of sections called frets. These are separated by a small metal bar. By pressing down on the string over the middle of a fret an plucking the same string a guitarist can produce a note.

The main problem that is faced by guitarists is that the same note can be played in different positions on the fretboard. For example, if you look at the picture on the left, you can see that the note A can be played on both the fifth fret of the E string (lowest string) and the open A (second string from the bottom). This is the same note and due to the way that guitars are played pieces can be made easier or harder by playing a note in certain location on the fretboard. This is where tabs are useful.

What do tabs look like?:

Tabs are used to indicate the location and fingering of certain notes rather than just displaying the pitch like standard music notation.

Depending on the instrument. Tab will be made up of a certain number of lines with each line indicating a string. (e.g. a standard guitar tab will have six lines and a standard bass tab will have 4 lines).

The lines indicate the strings from high to low. On the right is an extract from Where Is My Mind by The Pixies. The tab is below the musical notation. The top line indicates the top E string on the guitar. As you can see the tab starts on the 5th fret of the B string (second line from the top). From there the tabs are read like standard music notation from left to right with bar lines and repeats indicated.

On a guitar there are also markings indicating frets 3, 5, 7, 9, 12, 15, 17, 19 and 21 this provides a quick reference for guitarists so they can easily find the fret they want to play.

Tab notation:

Here are some playing techniques that guitarists use that you will find notated on tab. There is also a video that shows some of the techniques and how they are played.

Why do guitarists use tab?:

Pros

Very easy to read, any guitarist can read tab and understand how to play it.
Traditional notated music can be read by guitarists, but tabs make it easier for them to understand how to apply the music to the fretboard.
Tab also reduces having to remember which note goes with which fret. Which makes sight reading easier and quicker.
Traditional notation also doesn't clearly lay out the tuning necessary to play certain songs as some musicians choose to tune their guitar to different tunings other than standard tuning (e.g. drop D, open F and FACGCE)

Guitar tab also shows notation for specific guitar techniques such as slides, hammer on and pull offs.

Cons

Because tab only indicates the position of a note. There is no connection to music theory as none of the notes are actually written down along with the fret number. This means that there are no key signatures, intervals and accidentals marked. Some tabs will also come with the same part written in standard music notation but this doesn't always appear.
Tabs also don't often show rhythmic notation. Basic tabs will often just show the fret number and a basic rhythm (e.g. 8 numbers in a bar indicate a quaver rhythm).
Often genres such as jazz, folk and classical don't use tab so having an understanding of sheet music is necessary.
Other musicians can't read tab unless they have been taught how to read it so a guitarist trying to explain musical ideas through tab to a pianist would be difficult.