Bay the way I found this all about Bass Guitar playing.
Here's the link.
May be a little of subject though.
This part seems quite informative:-
If you have a four-stringed bass guitar, the bass guitar tabs will show four horizontal lines representing the four strings. The topmost string is the G string, followed by the D string, the A string, and lastly, the E string. If you see two numbers (one above the other) on one string, it indicates that the string is to be played simultaneously.
Bass guitar has 4 strings,well you learn something every day.
Malc.Learn to Play Guitar