A Meta refresh redirect is a client-side redirect. Unlike 301 and 302 redirects that happen on the web server, a meta refresh redirect instructs the web browser to go to a different web page after a specified time span.
<meta http-equiv="refresh" content="4; URL='https://ahrefs.com/blog/301-redirects/'" />
The number (4) is the amount of time in seconds before the browser redirects to the specified URL.
Meta refresh redirects are most commonly associated with a five-second countdown with the text "If you are not redirected in five seconds, click here."
Even though Google claims to treat the meta refresh redirects like any other redirect, those are not recommended to use apart from certain cases like when:
you cannot use an .htaccess file - in case, for instance, you are using a CMS which periodically overwrites your .htaccess file;
you want to redirect only a single file in a directory with multiple files.
In other cases using meta refresh redirect can lead to certain issues:
it can disorientate and confuse users. For example, if redirect happens too quickly (within 2-3 seconds), users of some browsers cannot click "Back" button; or if user experiences refresh he/she didn't initiate, one may get concerned about your website's security;
meta refresh redirects are quite often used by spammers to fool search engines, so if you use this option quite often, search engines may consider your site being spam and remove it from their index;
when used for redirection, meta refresh tag does not pass much or any link juice.
Thus, unless it is specifically needed on your pages, it is recommended to use a server-side 301 redirect instead.