Customizing Woo-commerce Check Out Page

I added a few fields to the Woo-commerce checkout form on my WordPress site and I would like to know which table in the MySQL Database this information is being posted to. Also, how do I access this table in my code if I wanted to tweak the form to check for a certain condition before it allows something to be done. I am customizing the form in the function.php file.

Any help would be highly appreciated.

https://wordpress.org/plugins/woocommerce/