Travertine is a compact variety of limestone that contains various sized holes that are formed as a result of the continual flow of water through the stone.  This creates bands that streak the travertine.    It is the holes that exist in the bands of travertine that create its unique qualities.  

Some travertine owners like to enjoy their stone in its natural state, enjoying the rough cut lines that streak the stone.  While others prefer to fill in the holes that are found in travertine with material like cement of synthetic resin.  

For those who appreciate travertine in its natural state, it is important to understand the need for specialized maintenance.  The holes that were created due to the water running through the travertine over time, are easy targets for dirt and grime.  If left untended, this can cause discoloration to the stone, detracting from the natural elegance of the travertine.