You can add custom fields to products to store data relevant to your business. These can be added through the ADMIN portal rather than requiring modifications or code-level changes.
Go to the DATA MANAGEMENT dropdown in ADMIN and select Custom Fields.
Then, from the dropdown on the page that appears, select Product. Enter the details of the field you wish to create including data type (text, date or numeric) and press Add New Column. The product will appear in the table below where you can edit if required.
On the product page, you will now notice your field will appear for each product. It also appears in the Product CSV mass upload mapping section in ADMIN>DATA MANAGEMENT> UPLOAD CSV