What are guitar tabs, and why is guitar tablature so important in guitar music?

Guitar tabs can be explained as easy to learn sheet music, but specifically for the guiar.  Symbols using letters and numbers corespond with the fret and string that must be held in order to produce the desired note.  Rather than depicing a music tone in the way traditional sheet music does, guitar tabs cutually represent the musical direction.  Guitar tabs date back many years and is actually an ancient system... but that is another topic.  Feel free to comment on that one :)

With guitar tabs, the vertical lines represent the strings on the fretboard of the guitar while the horizontal lines represent the frets themselves.  A six stringed guitar, naturally, will have 6 horizontal lines.  A bass guitar will only have 4.  Dots, numbers and other symbols are then placed on the lines to how finger position, hammer-ons, pull-offs, bends, slides, harmonics and vibrato.