A redirect is any method used where a user is taken to a different landing page than the one that they initially requested.
There are three common redirects which are used by SEOs:
301 redirects, or permanent redirects, divert the user and pass nearly all of the link authority from the original page to the new page. 301 redirects should be used when you update pages or urls to a permanent new home.
A 302 redirect, or temporary redirect, is supposed to be used when you move a landing page for a short period of time with the intention to move it back. However, there is some dispute about how much link authority is passed on through a 302 redirect – it was 0% but Google now claim that some link authority is passed on. To be safe it's best to stick to 301.
While the two redirects above are server-level redirects, a meta refresh works at page level in the users browser. They are most commonly associated with the "If you are not redirected in 5 seconds click here" instruction. Meta refreshes do pass some link authority on but are not recommended due to poor user experience.
The answer to this question from an SEO point of view is nearly always 301. No other type of redirect can be guaranteed to pass on the page and link authority you have worked hard to obtain and you could see a drop in rankings if you opt for another method.