Google accounts for 85% of all traffic in the UK, with Bing 10% and Yahoo 5%. This is the reason when we talk about search engines, we normally think in terms of Google. But we also consider others as every slice of traffic matters. For our purposes, we mostly refer to Google when talking about SEO.
Natural or organic traffic means unpaid traffic. If you type in a keyword phrase, you will usually find that the first few entries at the top of the result page are adverts. Every time a person clicks on one of these advertised links, the company which has placed the ad will be charged. How much these are charged will depend upon the keyword and the competition for this key word.
PPC is expensive and you wouldn’t know who is clicking on the links, and once your budget has gone, your advert disappears. That is why SEO is a better solution for the organisations who have smaller budgets.