I'm new to the Win32 API and the many new types begin to confuse me.
Some functions take 1-2
DWORD LPCWSTR LPBOOL
The Windows API was first created back in the 1980's, and has had to support several different CPU architectures and compilers over the years. They've gone from single-user single-process standalone systems to networked multi-user multi-core security-conscious systems. They had to work around issues with 16-bit vs. 32-bit processors, and now 64-bit processors. They had to work around issues with pre-ANSI C compilers. They had to support C++ compilers in the early unstandardized times. They had to deal with segmented memory. They had to support internationalization before Unicode existed. They had to support some source-level compatibility with MS-DOS, with OS/2, and with Mac OS. They've had to run on several generations of Intel chips, and PowerPC, and MIPS, and Alpha, and ARM. The same basic API is used on desktops, on servers, on mobile phones, and in embedded systems.
Back in the 1980's, C was considered to be a high-level language (yes, really!) and many people considered it good form to use abstract types rather than just specifying everything as a primitive
void *. Back when we didn't have IntelliSense and infotips and code browsers and online documentation and the like, such usage hints were helpful, and it made it easier to port code between different compilers and different programming languages.
Yes, it's a horrible mess, but that doesn't mean they did anything wrong.