SEO is what they call a "natural" or "organic" way to rise within search engines. Web site owners have to either spend the time to write content and find sites to link to them or pay someone to do it.
The alternative is to focus on the site's lead conversion and then pay for your web site position using PPC or Pay Per Click advertising. Search engines place ads on their search engine results for specific key words. They work with their customers so the ads are placed according to geographical location among other factors.
They charge an amount per user click. This means a site owner sets up a budget and manage how the ads show up on their search engine results. Every time a user sees the ad and clicks on it the search engine company subtract an amount from the budget. They leave it up to the web site to do the work of conversion. They do care what happens with every click because they make more money when ads are successful. Their goal is to place the ads in intuitive positions to drive traffic through the ads so they can get paid.
For those professionals who want a productive site but don't want to spend time on the SEO it is a good idea to design the site for great conversion and then spend the money on ad space.
Search engines charge varying amounts for click through links depending on the popularity of the keyword or phrase. Site owners may be charged anywhere from a few cents to several dollars per click depending on the market.