Ranking
The order in which individual web pages are returned in the SERPS for a given search query. Search engines rank the web pages based upon relevancy to your search terms according to their proprietary algorithm.

Reciprocal Link
Links to another website placed on your site in exchange for links back to your site from theirs. This is a proven way to build link popularity which is instrumental in getting high search engine rankings.

Redirect
A tactic sometimes used to send a user to a different page that the one she found in the SERPS. For example, a webmaster optimizes a web page for a very popular keyword. When a user finds the page by searching on that keyword, she is subsequently redirected to a different, possibly non-relevant page that the webmaster stands ready to make money from.

Re-submission
The process of submitting a web page to a search engine and then repeating the submission process - either a couple of times or regularly over a period of time. Contrary to popular belief, regular re-submission does not improve a page's ranking and is considered a form of spamdexing by most search engines.

Robot
A program used by a search engine to crawl the web in order to find, rank, and index new web pages.

Robots.txt / Robots Text File
A special file that is commonly used to exclude some or all robots from crawling certain files or directories on a website. This file should b placed in your website's root directory.