Exploring the Odoo application and module directory
In addition to the built-in Odoo modules and the various settings that can change the way Odoo functions, there is also a growing collection of custom Odoo modules written by the community. When you find a business requirement for which you believe you may need to do some custom module development, take the time to go to the Odoo application repository and search for modules that could perhaps fit the purpose. Even if the module is not exactly what you are looking for, there can often be a lot of valuable code in those modules that can help you with your own module development.
Note
You can find the Odoo application and module repository at https://www.odoo.com/apps.
Even more importantly, these applications are invaluable for studying how to build and customize applications in Odoo. When you get stuck trying to solve a development problem, the Odoo source code and the available applications that you can find in the Odoo application repository...