W10, 64 bit, all updates. Under Programs, I have 4 distinct Powershells listed.

1) Windows PowerShell
2) Windows PowerShell (x86)
3) Windows PowerShell ISE
4) Windows PowerShell ISE (x86)

What are the differences?

The versions without (x86) are 64-bit, the versions with (x86) are 32-bit.

Powershell is a text based interface like command prompt.

Powershell ISE (Integrated Scripting Environment) is a GUI interface that helps automate the process of creating scripts.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiPxbDQmbb0AhUClWoFHXEKAKwQFnoECBwQAw&url=https%3A%2F%2Fwww.javatpoint.com%2Fwindows-powershell-ise&usg=AOvVaw3E-kC-CIm0JcE5Q1UcP9Q2

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiPxbDQmbb0AhUClWoFHXEKAKwQFnoECAkQAQ&url=https%3A%2F%2Fdocs.microsoft.com%2Fen-us%2Fpowershell%2Fscripting%2Fwindows-powershell%2Fise%2Fintroducing-the-windows-powershell-ise&usg=AOvVaw1p9ve12WECs-mdaF2GTSzj

As a practical matter, what are the advantages and disadvantages, of having all four, on my computer? Although I'm reasonably computer literate, this seems overly complex.

Can command prompt (Admin) do the same things?

Quote:

As a practical matter, what are the advantages and disadvantages, of having all four, on my computer?

They are part of the Windows operating system, I recommend that you leave them alone. Deleting the ones you think you won't need won't improve the performance of your computer or free up vast amounts of space on your hard drive, if that's where you are going with this.

Powershell vs. Command Prompt
https://www.varonis.com/blog/powershell-vs-cmd/

I really had no intention of removing it.

Interesting article, but it begs the question, why are there 4 variants on my computer, and do I need all 4?

Microsoft deemed it necessary that you have all four. And most Windows users have never heard of Powershell.