I have a question about Program Files (x86)

As mentioned the "Program Files" folder is used for 64 bit applications while "Program Files (x86)" is used for 32 bit applications. An important reason for this is to separate 32 and 64 bit applications, many of which have the same folder and file names. Other methods could have been developed but when all the factors are considered, and there are many not mentioned in this thread, it appears the method used works very well.

What happens when an old 32 bit application installer that predates 64 bit Windows tries to create a folder in the "Program Files" folder? If something were not done this could overwrite 64 bit files stored there. What happens is that the file system silently redirects all such attempts to the "Program Files (x86)" folder. If the application later tries to access these files in "Program File" it will get them from "Program Files (x86)". This redirection only happens for 32 bit processes. A 32 bit process can temporarily disable this redirection but it has to be 64 bit aware to do that.

Having separate folders can be confusing but for the user everything just works.