What is the difference between x86_x64 and x64_x86 in MS Visual Studio Command Prompts?

Question

visual studio

I installed MS Visual Studio 2019 Community, my system is Windows 8.1 x64.
There was a need to compile something, through the command line, visual studio, in 32 bit (and then in 64 bit, too) and now I was interested in the question - in which command line better to compile it -
In "x86 Native Tools Command Prompt for VS 2019" or "x64_x86 Cross Tools Command Prompt for VS 2019" ?
What x86 means is now clear to everyone, but what does x64_x86 mean? From Microsoft comments you can read -
x64_x86 - Open Visual Studio 2019 Tools Command Prompt for targeting x86 with x64-hosted tools
That is, these are command prompt tools for compiling to 32 bits on x64 systems, i.e. compiles to 32 bit but will run on 64 bit systems, but not on 32 bit? And x86 is compilation in 32bit and for execution only on 32bit OS? But I already tried to somehow compile in x86 and then everything was executed on my 64-bit OS.
The same question and about - "x86_x64 Cross Tools Command Prompt for VS 2019" with a comment -
"Open Visual Studio 2019 Tools Command Prompt for targeting x64 with x86-hosted tools" - it's like this - it will compile to 64 bits and will run on 32 bit systems? Is it even possible?