I have both games in my library now but I don't know how they are different. Can somebody explain please?

From Redux page:
Remastered visuals, a remixed main theme, and compatibility with modern gaming PCs.
Challenging GOG Galaxy achievements for only the most skilled warriors.


Classic one runs thru DosBox

Thanks for the clarification :)

Heh forgot to write more. I installed the redux version aswell.
When you srtat it, it throws up a popup where you can select main game or from 2 expansions.
Main menu is modern and it runs natively, doesn't seem to use dosbox.
Textures are a bit modernized, but still look old-schooley