How do you know if you have found a niche when targeting keywords with PPC marketing?

I have been doing research and I have found keywords that pertain to my product and i am getting an average of 1,500 per keyword and most keywords have no competition and are only .05 cents according to google. Can anyone tell me what this means? Does this mean that I have found a market where no companies are? Or am I not understanding something about the google keyword tool.