Keywords are used to focus on your potential customers. It is used to get the exact location and position of your ads. The keywords are words or phrases that people use to find your site. Yahoo Bing Network or Google Adwords use to auction the spaces in the website in the form of ads. You need to bid against other bidders to get the space you want. The keyword bidding feature helps advertisers either increase the number of clicks or reduce the costs of keywords. While higher bids will generate more impressions, the CPC will also increase. Low bids will result in low impressions, but your CPC will also decrease. The good strategy is to place a bid that lie somewhere in between the higher and lower end.