What is 301 redirection?
Can't you just Google it? What do you need to know exactly?
This is from Wikipedia:
The HTTP response status code 301 Moved Permanently is used for permanent URL redirection, meaning current links or records using the URL that the response is received for should be updated.
It is permanent redirect the site,301 refers to the HTTP status code for this type of redirect.
Google, or your favorite search engine, is your friend, learn to use it.