Odoo is a fully-featured open source platform for building applications. Based on this core framework, a suite of integrated applications was built, covering all business areas from CRM and sales to stocks and accounting.
Beyond these out-of-the-box features, Odoo's framework was built with extensibility in mind. Modifications can be implemented as extension modules, to be applied as a layer on top on the existing modules being changed, without actually changing the original code. This provides a clean and easy-to-control customization approach.
This capability to combine several modules into feature-rich applications, along with the open source nature of Odoo, are probably important factors in the growth of the community around Odoo. In fact, there are thousands of community modules available for Odoo covering virtually every topic, and the number of people getting involved has been steadily growing every year.
Odoo 12 Development Essentials provides a step-by-step guide to Odoo development, allowing readers to quickly climb the learning curve and become productive in the Odoo application platform. At the same time, it tries to provide good reference materials, to be kept close to hand every time you are working with Odoo.