A URL redirect is generally a feature that takes a user to a different website than the one they had entered in their browser’s address bar or the URL that they had clicked on to visit. It is generally carried out on the web server side to allow visitors to browse a website when it is undergoing maintenance or restructuring (called Server-side URL redirection).
Client-side URL redirection (also called open redirection) on the other hand, is considered to be an input validation flaw that is generally discouraged in modern website development because malware or hackers can tell a web browser to redirect the user to a malicious website without the user’s knowledge. This tactic could be used for data phishing and to steal user credentials when logging into a lookalike site controlled by attackers that appears to be essentially identical to the website that the user intended to visit.