You can get additional information from customers during checkout Process?
This information may be used for different purposes such as to enhance your services, marketing and product related information.
There are different modules available in market which allows you to add custom input/output fields on checkout pages. order attributes Add-on for PrestaShop is one of the most effective plug-in to get valuable information. Prestashop order attributes
The supported fields are text field, text area, date, yes/no, multi-select, drop-down, checkbox, radio button, and message only. Validation is performed automatically.
Message only field allows you to display important information to customers on checkout page.
Checkbox, radio buttons allow you to understand your customers behavior.
You can learn where your customers came from by adding custom fields on checkout page.
You can also add ‘Refer a Friend’ text field where customers can recommend your product to their friends, which not only helps them but also provides you with leads.
You can also add delivery times and options etc
http://www.fmemodules.com/en/51-custom-fields.html