Wow64 (Win32 emulation on 64-bit Windows) refers to the software that permit the execution of 32-bit x86 applications on 64-bit Windows. It is implemented as a set of user-mode Dlls:
Wow64.dll: Manages process and thread creation, hooks exception dispatching and base system calls exported by Ntoskrnl.exe. It also implements file system redirection and registry redirection and reflection.
Wow64Cpu.dll: Manages the 32-bit CPU context of each running thread inside Wow64, and provides processor architecture-specific support for switching CPU mode from 32bit to 64-bit and vice versa.
Wow64Win.dll: Intercepts the GUI system calls exported by Win32k.sys.
The relationship of these Dlls is shown in Figure 3-31.
Figure 3-31. Wow64 architecture