In the Odoo framework, models are what hold and manage the data that make up your Odoo application. When you save a sales order in Odoo, the data for the sales order header is stored inside a model appropriately named sale.order. Individual data items, such as order date and customer address, are known as fields.

Models can also be linked and associated with other models. For example, the sale.order model is linked to the sale.order.line model by the ID of the sales order. In this chapter, we will be adding a few fields to the sale.order model inside Odoo.