In SEO and SEM terms, rank (or ranking, position) refers to where a website or page is ranked within search engine results.
For example, if your Web site is about microphones, when a person queries “microphones” in a search engine, your ranking indicates where in the search results your Web page is listed (e.g. within the top 5 results, on the first page, the 300th page and so on).
A webpage rank within a search engine is also commonly called a position.