An SEO URL provides both humans and search engines an easy-to-understand indication of what the destination page will be about. Search Engine Friendly URLs allows you to activate categories and product's SEO Keyword setting. For each product, category, brand or content page you can assign SEO keyword visible in url. This will better describe a product's page to visitors and search engines.
To use SEO URL's Apache module mod_rewrite must be installed and you need to rename the root htaccess.txt file to .htaccess
This file is located in public_html directory of the source code https://github.com/abantecart/abantecart-src/blob/master/public_html/.htaccess.txt
mod_rewrite is something that is installed on your server by your web host. You need to ask your host (or look in their help guide) to find out if you have it.
.htaccess is a configuration file for use on web servers running the Apache Web Server software.
Nginx configuration file extension is located in nginx.conf.txt file of public_html directory of the source code https://github.com/abantecart/abantecart-src/blob/master/public_html/nginx.conf.txt
Copy this configuration to your Nginx site configuration. Depending on the site configuration, you might need to alter rewrite rule.