Pods is a framework for WordPress that allows you to create, extend, manage, and deploy customized content types and fields.
If you need to add custom post types or taxonomies to WordPress and then extend them with a graphical User Interface (UI) and then want to add a nearly unlimited number of additional fields, then Pods might be the right choice for you. It also features relationships between content, so you can do one-to-many or many-to-many relationships and query easily for them with an easy to use low level API. Pods is mostly written as OOP software, so advanced developers will be able to quickly scan source code using their IDE.
Link to Pods homepage.