Odoo is an open source accounting software. With much more features than only accounting, such as warehouse management, project management, HR management etc.
CiviCRM is an open source software for non-profit and is great in membership management, donor management etc.
For one of our clients we have been working in integrating both CiviCRM and Odoo where Odoo is leading in the financial data and CiviCRM is leading in the contact and membership data.