In the SEO industry, a 'redirect' is a reference to a search engine friendly redirection from one web page or website to another web page or website.
If the address for a particular page or resource changes, it is always advisable to redirect search engines and visitors to the new address using a redirect. If the address for a resource changes and a redirect is not implemented, the user or search robot will encounter an error page, and not reach their desired destination.
Search engine friendly redirects are implemented by using a server status code. The status code for a search engine friendly redirect is '301,' so a redirect may also be called a 301 redirect, or a 301 search engine friendly redirect.