Tablature, Diagrams, and Copedents
Tablature is a simplified music notation system. It's been around for centuries and preceded our current classical notation system. It has been used primarily by guitarists in the last 40 years or so. Steel guitarists have also adopted it. Here's what it looks like:
The horizontal spaces between the lines represent the strings. The top one being string number 1 (the one furthest from the player). The numbers in the spaces represent the fret where the tone bar rests when that string is plucked. The letters next to that indicate any pedals or levers used (pedal and lever names are discussed in more depth in the copedents section of this site).
As you can see, there is no indication in tablature on how to play the rhythm of the piece. Also, suppose a violinist wanted to play a piece written for steel guitar, how would they do so without learning how to read steel guitar tablature? The limitations are clear, but there are benefits to tab. It is really easy to read and understand, and it can be a really quick way to get the general idea of how to play simple tunes.
Sometimes diagrams are used to explain musical ideas. These are usually used to show scale or chord patterns. Diagrams show the fret board with markings on it indicating where the notes are. Diagrams usually don't show rhythm or music as it moves through time, but rather show where a set of notes would be located on the instrument.
Here are two diagrams showing some possible locations of the C major scale notes on the PSG neck:
The numbers over the top are the fret numbers. The spaces between the lines are the strings. The note names are written in the spaces at their proper frets.
The steel guitarist's "copedent" is also a diagram conveying musical information. It is addressed in detail in the WHAT'S A COPEDENT section of this site.