This type of executables could be found inside the UEFI firmware. The UEFI firmware is stored in SPI flash memory, which is a chip soldered on a system’s motherboard. UEFI firmware is very modular: it usually contains dozens, if not hundreds, of executables. To store all these separates files, the firmware is laid out in volumes using the Firmware File System (FFS), a file system specifically designed to store firmware images. The volumes contain files that are identified by GUIDs and each of these files contain one or more sections holding the data. One of these sections contains the actual executable image. Most of the executable images follow the PE format. However, some of them follow the TE format.
The Terse Executable (TE) image format was created as a mechanism to reduce the overhead of the PE/COFF headers in PE32/PE32+ images, resulting in a corresponding reduction of image sizes for executables running in the PI (Platform Initialization) Architecture environment. Reducing image size provides an opportunity for use of a smaller system flash part.
So the TE format is basically a stripped version of PE.
This page hosts a formal specification of TE (Terse Executable) file using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.