To get a complete development environment for Oracle ADF please download Oracle JDeveloper 12c - this will include everything you need in order to build and test Oracle ADF applications. If you prefer to use Eclipse based IDE for your development download Oracle Enterprise Pack for Eclipse that provides support for ADF Faces and ADF Controller development.
Note - Oracle ADF 11.1.2.* Application Development Runtimes are provided as a patch for the complete Oracle ADF Runtime and is available through Oracle Support. Read the release notes for your specific version for further information.
This is the FMW Infrastructure and it functions as both the ADF Runtime distribution as well as a prerequisite for other FMW products.