Search engine optimization (SEO) as a subset of search engine marketing seeks to improve the number and quality of visitors to a web site from "natural" ("organic" or "algorithmic") search results. The quality of visitor traffic can be measured by how often a visitor using a specific keyword leads to a desired conversion action, such as making a purchase or requesting further information. SEO is often very technical and not transparent for the average person. Some of the work of SEO's is not even visible to the human eyes, which supports the misconception that SEO is a way of "gaming" the search engines, which gives this young and mostly misunderstood industry sometimes a bad name.