Tapping is a style of playing bass where you just push down the fret with a finger instead of doing the whole plucking style.  Your left hand often hits the bass notes or root notes while your right hand oftn does the melody.  Here is a quick example.  

L= left hand
R= right hand

G---------------------------------16-18--------16-19/18
D-------16-18--------16-18-----14-----------14---------
A----14-----------14--------12-----------12------------
E-12-----------12--------------------------------------
  L  L  L  R   L  L  L  R   L  L  L  R   L  L  L  R  R

Just try this example a couple of times. Tapping is really cool to use when soloing also.  You can pick up some pretty good speed with it also.  You can pretty much do anything with tapping.  I hope this helps out!  I have some other tabs so if you want to go check them out then that would be great!
thanks