See the Microsoft Portable Executable and Common Object File Format Specification for information on PE/COFF images.
The Platform Initialization Specification, Volume 1 defines the data structure for terse executables.
The Platform Initialization Specification, Volume 3 defines the data structures for UEFI/ PI images.
The build tools are required to support IFR op-codes defined in the UEFI specifications. The EDK II implementation for Visual Forms Representation (VFR) syntax is documented in the VFR specification available from the TianoCore EDK II web-site, under EDK II Specifications.