What is the role of the .htaccess file in WordPress, and how can a corrupted file cause a 500 error?

The `.htaccess` file controls how Apache handles requests to your website. Incorrect directives, such as rewrite rules, can lead to a 500 error. Try renaming your `.htaccess` file to something like `.htaccess_old`. If your site works after renaming, the old file was the problem. You can then regenerate a new `.htaccess` file by going to Settings > Permalinks in your WordPress dashboard and clicking 'Save Changes'.