A 302 "Temporary Redirect" is a common method for redirecting from one URL to another.
The number 302 refers to the HTTP Status code value found in the HTTP response header that is sent by the web server in order to let the client know that the requested resource has moved temporarily, and can be found at a new location during this time. Later, it will return to its original place.
In contrast to a 301 redirect, a 302 redirect is interpreted by search engines as a temporary phenomena that could change back at any time. Because of this, search engines will usually not remove the original URL from their index, and will not pass any link juice to the target URL since they expect this situation to be temporary.
This means that if a high-ranking URL moves to a new domain or a new location somewhere else on your site, all of the hard work you've put into getting the first URL ranking well will not be passed on to the new URL location. This can be disastrous for your site's rankings, and therefore is not advised in most situations.
Actually, the correct standard interpretation of 302 is "Found". However, in practice, it is seldom used this way, so this method is ignored for now.