The Global Redirect module has three main features:
If you search around the Web for Drupal SEO tutorials, many people recommend using mod_rewrite rules in an .htaccess file to deal with issues like removing trailing slashes. But on sites that also have non-Drupal content, you may have URLs that do have trailing slashes.
A slash is the symbol for a directory. For example, in the URL http://example.com/ the trailing slash is the symbol for the root directory of example.com. If you leave the trailing slash off, the server will add it. If you request a physical directory on a Drupal site (or any site) like http://example.com/modules the server will correct you by appending the trailing slash: http://example.com/modules/. If you have non-Drupal content on your server—perhaps a WordPress blog at http://example.com/software/—you will have URLs with trailing slashes. The WordPress blog would not be located at http://example.com/software, it would be located at http://example.com/software/. You would not want to remove trailing slashes from all URLs.
That is why the Global Redirect module is a good option. It will only remove trailing slashes from URLs that are handled by Drupal.