This sets the maximum time in seconds a script is allowed to run before it is terminated by the parser. This helps prevent scripts from tying up the server. The default setting is 30 and setting a different max_execution_time can help if you're seeing an fatal error on your site when trying to install/update a plugin or maybe upload a file. It's a PHP directive and can be set on the PHP page in the Hosting Platform.
Here's a link to our guide on accessing the PHP page: